Do Regen, Medica II's, and Asylum's regen effect all stack?

[MoroMurasaki]

Also, for 8/24mans, yes, multiple regen effects all stack, with the possible exception of Asylum. (never tested that one)

Also worth noting that Aspected Benefic's regen does not stack with another Aspected Benefic, it works like a shield where only the most recent one exists

In terms of HoT uptimes strive to do the bulk of your healing through your regens ticking. Like if you pop Medica II after raidwide damage and that brings everyone up to above 70% let the ticks from Medica II top people off instead of casting another healing spell. You need to be sure they won't need that 30% health immediately to survive another hit but in casual content I can't think of many situations where that's the case.