Go for something other than telepath. Shapers are insanely good no matter what you're up against, and any telepath with Expanded Knowledge (Astral Construct) can hold its own (not to mention you can simply hunt down a critter to use as a meat shield and Dominate it for your own purposes; if it dies, Dominate another one).
Also, you could go thrallherd as your PrC, and send your minions after the undead while you hang back.
If you could avoid those negative levels, a druid should be able to blow anyone but other T1 classes away. They're the most well-rounded and powerful class in core so long as you're not especially optimizing well, though that does depend on how you play. Do you have Natural Spell? If so, that's all the optimizing you need. Just stay in a wild shaped form that can avoid getting hit (such as a bird), and cast battlefield control spells before sending in your animal companion to kill everything in sight. If your buddy gets level drained, either release it from your service while it recuperates or use your ability to cast to remove the negative levels.
Seriously, druids are insanely powerful if you play to their strengths.
But if you REALLY want to change your character, try playing a warforged shaper. They're immune to a lot of undead abilities and can destroy undead with impunity using astral constructs and other metacreativity powers.
Also, see what Solo said.
[edit] Either way, make sure you have some way of affecting incorporeal undead. There are magic items that do this, and any [force] effect or abjuration effect does too.
