I wouldn't read too much into the Infect thing - the Infect deck at the Modern PT is likely something they're not happy about.
Griselbrand gives you a T2 kill off Goryo's by letting you go infinite w/ Fury of the Horde. It's inconsistent but can one-shot you.
edit: Counterspell is not the answer. Mana Leak/Remand are just fine. It's other things that are the issue. The large issue with Modern is that they never actually banned the "T3" cards. They instead banned random crap and didn't go deep enough with the cuts initially, leading us to where we are today. You could unban AV, Jace, and BBE and it wouldn't do a whole lot to the format.
They probably aren't. But when
More like they just printed a +6/+6 for G
is the case, maybe it's time to just ban that stupid card.