As a few predecessors before me, I am a fan of Diminishing Returns. I'd go even further: not just let Traya stack Tenacity, but much rather lower the effects and probabilitys (exponentially) of all sorts of TM gain mechanics (per round), Prot stacking mechanics (prot stacking getting exponentially less efficient) and debuff probability decrease - all within ONE round. This would prevent so many problems in this game. And yes, of course it would hurt precious beasts right now (Nest, HT, Traya, C3PO, Finn,...) but not fundamentally change their mechanic!