First of all I want to precise that I'm a bio terran player so sorry in advance if the following suggestions seems a little biased.
When I saw all the complains about the sh nerf I was just telling myself that it was to early for zergs to whine and that zerg would figure something out on their own. That's exactly what some people were saying during the era of gglords and imbators and it was exactly what some other people where saying during the msc completely broken.
The fact is that if we don't try to anticipate the meta (to some extends) we are just going to have some useless, none fun game to watch for months and I do not want that.
Why the compensations?
Before swarmhost (end of wol), people dealt with mech in different way. The most common mech build was the mvp 3 cc/hellion/banshee and double upgrade (there was a similar bio build that made both build more powerful). Zergs were able to analyse the problem and found different ways to deal with it, passive with a big composition switches or some early roaches(sometime with hydras) timings. Those games with the roaches doom drop where so funny to watch.
But a few balance changes occurred since then. The banshee cloak cost decrease, hellbat arrived, thor 250 mm canon, nerf of the fungal and infested terran , upgraded air/ground combined, mines arrived etc etc. Of course zergs got their own buffs but they where created to counter the bio.
My suggestions
The raven: I believe that this is one of the more interesting unit of the game... except...when the terran is massing them, then it become painfully stupid.
TvT is so fun to watch and play right know because of it, it is even really good in the other match up too. It can be a defensive unit (pdd, turret) a great harass unit (turret in mineral lines, bombing the workers whhile droppîng elsewhere etc) and a cool support unit because of the detection (creep, borrow, dts). Look at this move and tell me that this is not why you are watching sc;
.
The problem is that terran are not making it in those match-up because of the big techlab restriction.
This is how, I think, this unit could be fix, make it so terran player can only make one at a time (like the msc for protoss). That would mean a pretty big nerf. This is why we can at the same time buff the unit itself, for example, make it easier to build or decrease its cost. The best idea imo would be to build it from an OC if the starport is already build. We could see a raven every game and it would suppress the problem of mass ravens.
I know that a lot of people will counter this suggestion by saying that this is not warcraft (i never played it), but the idea is not to make the raven a terran hero. I believe that this change will increase the skillgap in the good way. Seeing pro player micro and multitask with it will be so cool.
The infestors: It used to be a useful spell caster with no auto attacks. Now they are quite boring, zergs make them when they are ahead or for the the money fungal when they are too far behind.
My idea is to buff neutral parasite. Seriously, I don't think this spell was used once since hots (even before that I believe). Make it possible to use it against any units, suppress the upgrade so we can use the spell directly, increase the range . If the unit is then to strong, a good way to balance it would be to nerf the infested units by removing the attack upgrades during the infestation or simply decrease the time of the infestation.
Overlords: I also think that overlord drops are underused lately. I think a good idea would be to create another upgrade (lair) to increase their armors. I missed the roach doom drop or seeing baneling being dropped on the top of death balls.