Problem is that tri hero builds aren't uncommon, micro tax is not suitable as an argument. True experience mechanics can mean that heroes you may want to level are deprived of exp but there are level benchmarks that you want to achieve with most heroes and after that, the experience gain isn't as important so you would expect all players to grab 3 heroes at SOME point in any match longer than 15 minutes. But we do not see this. Instead we sometimes see single hero builds in matches that last 30 minutes, and sometimes tri heroes in 12 minute matches.
Okay. So building tigers from t1 should be a-okay balance wise since at most players will only build one or two, and they're sacrificing a whole 2-3 infantry squads to build it.
Or you already lost a heavy tank to your opponent and those forces were produced originally to counter it? Or you have been dominating in the tank department while your opponent has stronger infantry so generalist tanks aren't necessary for him?
Oh. Well if my heavy forced my opponent to invest 2-3 times the resources into countering it I probably should start pumping infantry since it already did it's job handily. It's not like they'll have much pop left to counter invest with and close the game.