NOTE this is ONLY in MY opinion.
3 overpowered
nitro serebii egon
3 underpowered
TA is not as efficient as other heroes in late game monta unless your with a golem. Its hard to actually use it well if your against very experienced player who can see through cloak
lastly, i think is queen, Like i said, late game wise, other heroes are much better choice in my opinion, if someone has something to differ, i am willing to learn
3fun hero
i simply love tassadar. When i am in a pub game, i love item whoring it just to see it kill zealots in a whisp. But it's only for fun. Then i like mass queen. You heard me, mass queen, there was one game i bought about 18 queens and i made an army of spines but never do this in a real game. Lol, only for fun. Thirdly, i like using TA a lot. It's not good for late games, but normally when i random it i get very happy since it is a fun hero to item whore. But still working on controlling maim. Have gotten better
Techs. The tech i always prefer is human. Because i use it too much
I really do not have a *best* tier i only have the best of each tier imo
Best tier 1 for me is Zealots. If your in a inhouse or tourny, putting your zealots in front as a tank with marauders as a back up or simply any range is well done. But obviously, not that useful in late games when all the tier 4 +5 come in
Best Tier 2 for me is marauders. I hate roaches with a passion. Not that their weak, just dont like them. For one thing their ability to burrow, when they move you can see the shadows -_- stalkers are nice, but i like marauders for their stimpack
Best tier 3 for me is hydras. High attack, low defense, my style of fighting. Archons are good for tanking, their like the upgraded version of the prisoner ones meant for tanking but have splash dmg which is nice. Hellions.. how should i judge them? good for surrounding heroes. But i dont think they can outcome hydras. Who knows, i think i am gonna try it out. Since hellion surround is pretty nice
Best Tier 4 is definitely immortals or thor. This depends on which of the two techs i picked in the first place. Ultralisk are like the third version of tanking. Along with splash, but they have a huge upgrade in defense from hydras to it. Which is also considerablely nice.
Best Tier 5 Would be siege tanks for me. I personally think colossus should be better since i love them A LOT better. But i get much better results from using siege tanks

brutalisk... EXTREME high attack. EXTREME high defense. But walks so slow and so big and so hard to stack and attacks very slow. But i guess with the combo of speed scroll+invis + hero buffs it can be very rewarding as well. But personally i like to get artifact than getting brutals. Just a personal thing.
But those are my favorite. Anyone got theirs to share?