Hello Shawtay,
For the moment they didnt say anything about adding new charms, im 14k points charms on my Main RP, i have all damage runes and some utility runes and i still having 4k free (im still waiting for them to add something usefull).
I hope in the future they add some other charms to the game.
Anyway, elemental charms + Low blow are extremly goods in high respawns. That means that probably if they add any "defensive charm" to game, people will still using elementals charms.
5% of max hp of the monster, make insane diference in late game hunts.
I hope i helped u, and they add something in future!
Gretings, Gleemody