Thing is winning with something (ex: Nova, Hammer) does not make it good. For us to get that win we had to draft from pick 1 in a very specific and hardlined way and had to play entire parts of the game in unique ways because of that pick.
If you want to play something unusual go to town. Just know what YOU need to do to make it work, and if you know what your allies need to do help them out. Most importantly, know when making that pick forces your team to give up too much to be worth it.
As for Hammer in particular, she is insta viable in any meta where you can only tri lane and roam lanes are dead. That was the case a few months back. All the melee assassin's that roamed sucked and so did tyrande and super tanks. When that meta hit Hammer was top notch. However in current affairs where Tyrande is literally everywhere along with Muradin, you just gonna get hard camped by a smart and coordinated team. If the opponent is playing a tri lane comp, Hammer is actually a very strong pick in HL.
Never pick Hammer on Tomb tho, that is just THE WORST map ever for her.
Random thoughts I know, but it's like 6:30 AM and I'm waiting up for something so hope my random tired rambling made sense.