Is it the first Telkine I am assuming. Is he killing you or you just not damaging him? One problem with the first telkine is he charms your summons. Maybe your core dweller is hurting you.
What is your build so far?
TitanCalc by stonedonkey - A Titan Quest Calculator
The link takes you too titancalc a userfriendly way to plan out a build. You can post it on GB by going to the bottom link once you fill out the titancalc form. Copy and paste the bottom link (not the top).
When I have played TQ I just keep whacking at the telkines and drink potions. Works for normal mode for the most part.