Whichever way these Talents work, for both Temp Health and Grimoire curse, I find the result questionable.
Letting THP affect them, like things seem to be now, makes them unreliable, but usable (and maybe even useful, depending on the particular Talent) fallback abilities. Similarly, letting Curse affect them can make them very hard to activate, with hits being either weak enough to ignore and immediately recover with THP or strong enough to down you straight away (or at least put you into immediate danger for a while, mitigating any advantage the Talents may give).
On the other hand, tying them to actual Health would likely make them highly abusable. Merc staying under 50% (real) Health and filling up with THP like a Zealot? No problem at all, with his Career Skill and huge cleave. Pyromancer going around with Grims and no or limited Curse Resistance? Nice, effectively permanent spell charge speed bonus. So if this were to be the case, they would need other methods to balance the abilities (and would partially negate the whole point of the health limitation to begin with). Also, as Waystalker’s Daughter of the hunt relies on being above a health threshold, it would become nearly or completely impossible to keep active at certain situations.
So I don’t think either version (for Curse or THP) is good for all Talents and abilities. They maybe could use a case-by-case check, but that would also reduce the internal consistency of the abilities. I find it somewhat acceptable that the Zealot’s ability works differently from the rest as it’s his primary Passive, not a Talent (though I find it somewhat too strong), but I do think that the Talents should have a consistency to them.