Trygon is yeah, but no better than a 3+ save and 5 wounds at 300 points?
I would rather spend under that for a slower 2+ save Carni with the same survivability stat-line (7 tough/5 wound/2+ save...I don't generally waste points on regen, but that makes a carni even more survivable).
Coupled with Size (it's actually easier to get a cover save for a 'fex than a trygon) they would have to ramp UP the trygon to make it worth while (and get rid of the DS only option...)
Now Carni squads are SCARY! (though I missed that part of the rumor?)