Thanks to you both.

playing with the talent calculator for the lock and following Purpleflavor’s advice, I end up with something like this : https://classicdb.ch/?talent#IZfgVzM0oZEx0xbMzx

seems fairly optimized towards hellfire while keeping a good dps with shadow bolt. Just wondering though if Aftermath (eg dazing mobs) really helps during aoe phases.

as for mages, I understand from daviddoran that arcane may become viable at 40, in the meanwhile frost is probably still better. Do you think tweaking my current build (which is mostly frost but includes arcane subtlety) to add improved arcane explosion is worth and would make any significant difference ?

thanks