You can get the
Official Strategy Guide from here <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
and also, Fergus only heals himself once IIRC. You can try strategies like, sneaking up to him, hit and run, ranged attacks etc.
The "Lead" character who's portrait has the gold edging (the other will be plain white), is the character that Fergus will attack, so if your one character is weaker (or takes damage easier) than the other, keep this in mind. You can change the "leader" by pressing F5 and Select both Characters by pressing F4.