I am a huge lore nerd and when the Psijic Order was introduced with the Summerset expansion I really embraced it on my main. Psijic outfits, mount, emotes, mementos, the works! However, the Psijic skills themselves, while absolutely beautiful, are pretty useless and not really viable for most builds maybe with the exception of Imbue Weapon. To that end I think it would be really cool to change one of the two morphs of the Mend Wounds ability to deal damage instead of healing. In it's current state the ability is not being used because there are much better healing options and it can't even be used at all by solo players since you can't use it on yourself. And it's a real shame too because it is a gorgeous ability, especially the modified heavy attack.
The change makes sense not just from a gameplay perspective but from a lore one too because the Psijic Order is all about temporal magic and it is fitting for an ability that mends wounds to also be able to unravel flesh if cast in reverse. And since the other morph will retain the original healing aspect of the spell nothing is lost while a great deal is gained.
I would also advance a similar argument for one of the Time Stop morphs i.e. instead of freezing time in the bubble, you speed it up, prematurely aging enemies and thus damaging them. That way there is a Psijic AoE damaging ability as well. I really don't see any downsides to this and I think it would really revitalize the entire Psijic Skill Line.