They refuse to overkill.
If you target an scv with 12 sieged tanks, only 1 will fire and kill the scv.
If you target a CC with 12 sieged tanks, they will all fire on the first volley, and on the second volley only enough will fire to finish the CC off.
I tested with many units, and it appears the group of tanks calculates how many will be required to kill the target in the smallest number of volleys, and only those tanks engage.
This is pretty cool, and I found that all units with instant hit attacks do this.(tanks,ghosts,rines,the flying think that's hotkey is v)
The new firing calculation shouldn't effect rines or the V things much, due to their high rate of fire (their firing gets out of sync anyway) but just by itself it should make siege tanks much more powerful in masses. The old tactic of mixing in workers and such as cannon fodder will be far less effective, as each one will only absorb 1 tank hit instead of the several they would in sc1.
SOOOOO, I was like, "how can I, take advantage of this?"
Well, I found a new and handy trick. It turn out if you hold the shift key while queuing up a chain of attacks, the tanks will intelligently distribute their fire among them very fast. The game will check for how many tanks it needs to kill the first target, allocate this number, then move to the next queued target nearly instantly, allocate enough for that, then on to the next target...etc.
The result is that instead of unleashing 10 tanks shots on the first marine, cooldown, 10 tank shots on the second marine, cooldown...etc..
The tanks will instead allocate one tank for each shift clicked marine, and rape all 10 of them all in about 1 second.
Try it!
Siege 4-10 tanks up in a pile, within their range build a barracks and position 6 rines far enough apart that they wont be splashed, shift queue an attack chain starting with the rax and then going through each marine,
Result: Tanks fire a few volleys to kill the rax, then quickly gun down the marines like a machine gun with one shot for each .
The exact same thing can be done with ghosts (replacing the tanks, not the rines lol)
I don't think any other races have instant hit attacks,maybe immortals? But I think this is going to be most effective by far with tanks due to their long cooldown and huge damage.
moral, shift key is imba
jesus that was long
WHY THE QUEUING?
+ Show Spoiler +
OK guys, let me explain
THE REASON FOR THE SHIFT-QUEUING
IF, you are being attacked and you DO NOT target your tanks at all
THEN
Tanks will semi-randomly attack units coming into their range BUT never overkill, if 10 units that take 2 shots each to kill are attacking 10 tanks.
THE RESULT: Possible outcomes are the tanks target all ten and bring them all to 50% health (worst possible), they double target 5 enemies and kill 5 (best possible), or any semi-random combination in between these examples.
IF, you are being attacked and you NON-QUEUE target your tanks as fast as you can
THEN
Tanks will double target each unit you manually click and kill it.Obviously you will target five enemies and kill these five. HOWEVER, you cannot click nearly as fast as the computer can process targets, you will end up spamming right click moving from unit to unit for the entire battle, and if you are not clicking on the next unit you want killed by the time the first target is killed, the tanks will fire randomly.
THE RESULT: You will end up killing 5 units guaranteed, BUT much slower than the computer can process targets, easy to mess up, and difficult. Try this, it really doesn't work well unless you have the mouse accuracy of Legolas.
IF, you are being attacked and you QUEUE target your tanks as fast as you can.
THEN
The tanks will cycle through your queued targets MUCH faster without any possibility of mistake. In order to get a head start on the tanks firing, it is easier to start on a target that will take at least a whole volley to kill (say, a colossus), then queue up a chain of units, this will allow you to get well ahead of the tanks during the cool down.
RESULT: With the first volley 5 units are killed machine gun style (as fast as the tanks can retarget themselves), and 5 units are already queued up to be instantly killed on the second volley. MUCH better.
SUMMARY
1. With NO targeting tanks will not waste shots, and they will be very fast, but they will pick targets poorly.
2. With STANDARD right-click targeting tanks may waste shots based on human error, target slowly, but will pick targets correctly. Like I said, this really doesn't work,it's just frantic spamming due to the unpredictable cooldowns of large tank groups. Exactly like target firing tanks in Sc1, it was only done at the start of battle or to kill super high value units. Compare this to the efficiency of...
3. With SHIFT-QUEUED targeting tanks will never waste a shot, will switch targets instantly, and pick targets perfectly. raep
THE REASON FOR THE SHIFT-QUEUING
IF, you are being attacked and you DO NOT target your tanks at all
THEN
Tanks will semi-randomly attack units coming into their range BUT never overkill, if 10 units that take 2 shots each to kill are attacking 10 tanks.
THE RESULT: Possible outcomes are the tanks target all ten and bring them all to 50% health (worst possible), they double target 5 enemies and kill 5 (best possible), or any semi-random combination in between these examples.
IF, you are being attacked and you NON-QUEUE target your tanks as fast as you can
THEN
Tanks will double target each unit you manually click and kill it.Obviously you will target five enemies and kill these five. HOWEVER, you cannot click nearly as fast as the computer can process targets, you will end up spamming right click moving from unit to unit for the entire battle, and if you are not clicking on the next unit you want killed by the time the first target is killed, the tanks will fire randomly.
THE RESULT: You will end up killing 5 units guaranteed, BUT much slower than the computer can process targets, easy to mess up, and difficult. Try this, it really doesn't work well unless you have the mouse accuracy of Legolas.
IF, you are being attacked and you QUEUE target your tanks as fast as you can.
THEN
The tanks will cycle through your queued targets MUCH faster without any possibility of mistake. In order to get a head start on the tanks firing, it is easier to start on a target that will take at least a whole volley to kill (say, a colossus), then queue up a chain of units, this will allow you to get well ahead of the tanks during the cool down.
RESULT: With the first volley 5 units are killed machine gun style (as fast as the tanks can retarget themselves), and 5 units are already queued up to be instantly killed on the second volley. MUCH better.
SUMMARY
1. With NO targeting tanks will not waste shots, and they will be very fast, but they will pick targets poorly.
2. With STANDARD right-click targeting tanks may waste shots based on human error, target slowly, but will pick targets correctly. Like I said, this really doesn't work,it's just frantic spamming due to the unpredictable cooldowns of large tank groups. Exactly like target firing tanks in Sc1, it was only done at the start of battle or to kill super high value units. Compare this to the efficiency of...
3. With SHIFT-QUEUED targeting tanks will never waste a shot, will switch targets instantly, and pick targets perfectly. raep
Video: Thanks JoshSuth! Here is the basic idea in demo.
Keep in mind that with these 7 tanks he could have killed 4 more marines in the second marine volley
+ Show Spoiler +
http://www.youtube.com/watch?v=cK9nGsLkTCo&feature=player_embedded