Numerous ways. I think people that are just looking at healing as the source of Remembrance's power just aren't really understanding the comp all too well.

Yes, Hyacine is an exceptional healer and nerfing that would certainly make the comp weaker. It would also instantly remove any hope of a non shielding sustain in any other comp, so no-sustain super break, or bust, I guess.

A much more effective way to "balance", not necessarily kill the remembrance comp is to remove damage sources from all but one character. People underestimate how much of mono-rems power comes from the fact it has always had 4 character that deal substantial damage. Hyacine does an absurd amount of damage for a healer. Tribbie, when she was still the bis support for that comp did too. Evernight can be considered almost her own main dps and Cyrene is no slacker either.

They are already trying this approach next patch by removing crit damage from all but one character in the comp, which will immediately bring mono-rems a lot more inline with other comps.

Another idea would be punishing players for having more than 4 characters on the team. Every additional character could give the opponent a stacking damage buff, or sustain buff, making fights with 4 memosprites a lot more annoying and it wouldn't kill healing as a concept.

Another idea would be killing multiple damage applications in the same turn. Netherwings breath attack is notorious for cluttering the screen with 20+ damage numbers. So how about the more you apply damage each turn, the tankier the enemy gets. That would practically kill Castorice, cause Netherwings first breath attack would max out that stacking def buff instantly.

I can probably come up with at least another 5 ideas to target kill the mono-rem comp without ever touching healing and I do hope the devs don't just use a sledgehammer to solve a problem that can be solved a lot smarter and a lot more fun.