Daedroths do not use magic
Daedroths in vanilla Morrowind were tough because of their ranged spell attacks. They typically used http://elderscrolls.wikia.com/wiki/Poisonbloom and that made them really tough, especially in confined spaces like ancestral tombs where the spell is really hard to dodge because of its area effect.
According to http://elderscrolls.wikia.com/wiki/Daedroth_%28Morrowind%29 daedroths can also shield and heal themselves.
However, in OpenMW v0.32 Daedroths use no magic whatsoever and that makes them fairly weak opponents.
(RM-2002 from redmine: created on 2014-10-11 by Sergey "Shnatsel" Davidoff, , closed on 2014-10-11 by nobody, duplicates #1856 (closed))