It is precisely because the vasari players can have extremely tough anti bomber support with only 3 tech labs (phasic trap) and their strong starbase, and tech level 1 repair structures.  Then throw in a phase jump destabilizer and you have a sick defense that will stay strong even in a 2v1 situation.  you only have a chance 2v1 against this if the vasari starbase hasn't been upgraded health/ weapon wise to lvl 2 on both.   

Best way to deal with this is to leave one ally to guard/scout the vasari world and watch for fleet buildup and hit them with culture, killing their constructors if you can to stop them from countering you (with phasic trap this becomes almost impossible, but you can try).

Tec can go early ogrovs, yet that will seriously hamper their ability to actually participate in any other useful function in the game for a long time.  Its usually better to take your 2v1 somewhere else and kick the crap out of that front while you build an occupation/defense force to let the culture do its work on the vasari HW.

Main reason the vasa defences hard to crack is because their sb is fucking mobile...its usually moves towards the attacker and fubar's hes sieging/bombing plans

I just imagined a medieval fortress moving towards a sieging army and rolling over them