Yeah, I am really surprised more people don't go Brummbar even in 1's, it's absurdly strong against infantry. Kicked my ass the few times it's been used against me. People seem to be allergic to Tier 4 in 1v1 though.
I guess that is just the nature of 1v1. It's risky to skip t3 as you might get overrun by T70s, shermans or cromwells.
In 2v2 and upwards, everyone and their mother goes Brummbar atm... which is getting a bit tiresome. Thank god Brummbar gets nerfed very soon.