Are we sure that is still the case for healing breath though? I mean npcs in battles generate cure enmity now as do trusts... I hear of people using auto cure cheats for enmity... they could've easily changed it... I'll probably get around to testing it eventually but my main focus is on pup right now which is a rather large amount of things to test with all the changes and general lack of posted testing.
Regardless my first idea was actually getting hate the same way melees do... dealing dmg minus the ws. Basically constantly spirit link over some hastes and marches some ja haste (need to test if hasso works) and some other buffs and watch the wyvern melee as fast as well buffed melees. Then give them tons of dt partly to keep them alive but largely to stem the loss of enmity from dmg to compensate for the lesser generation. Still a work in progress and it's largely a thought experiment and will probably be cotanking at best but a lot of pet strategies often include some bouncing as long as it's kept off the players and less of the directed dmg goes to the less defensive pets it's fine