Daedric mines are an area control tool. They deal reasonable damage ( especially if multiple mines are hit at once) and provide a short root on top.
They are not made to blow up the opponent in suprise, but instead give the sorcerer an area in which he can operate to set up his spells and provide some defense through their sheer threat.

Use daedric tomb. It's super spammable does the same damage as frags and in pvp just hm chuck it on those annoying DKs that perma block and watch it rinse them. Instant arming is much better than that crappy ring that you can see a mile off.