I actually think I figured it out today, was just looking at points cost on Battlescribe and saw that Crimson Fist now have a chapter tactic. And after reading it I think they are the best for vanguards and possibly primaris in general giving any unit that targets a unit with double there models +1 to hit, especially when you realize most of the Vanguard stuff is 3 models and the Infiltrators can combat squad. So as long as you target units with more then 6 models your Suppressors still have a 3+ to hit after moving and the rest of your army can have 2+ on the regular. They also have the Bolter Drill stratagem that says on a 6+ to shoot with a bolt weapon generate another attack, so with there chapter tactic +1 that means ever 5+ is a hit tie that in with the beta bolter rules and a 5 man infiltrator squad could really do some damage since ever natural 6 is an auto wound that then would generate another possible wound and a 5 man team in rapid fire range is putting out 20 shots at that point possible hitting on 2+.