Maybe Stilian should use his illusions and party buffs more...
Beguilers aren't really cut out to be agressive casters. They can shape the flow of events to a certain degree, but they can't be expected to be the matchwinner in every combat, regardless of what they're facing. They're not Wizards or Sorcerers, they work more on a low-key style.
Now by your description that seems to be Stilian's style, too, so I'd recommend sticking by your guns and play to your strengths. And maybe, if all you encounter are mindless or high-Will foes, you should have a little talk with your DM and tell him you'd like to be able to shine from time to time, too.
If you're set on getting a means of really hurting your opponents, nothing beats getting additional spells known for a Beguiler:
You might be able to convince your DM that the Extra Spell feat allows you to choose one extra spell known from any list - take Call Lightning or Enervation or Wings of Flurry or Slay Living, or whatever else strikes your fancy.
Another thing of note is that there are some Prestige Classes expand your spells known list (the Sandshaper PrC from the Sandstorm supplement being a prime example).
Also, have a look into Magic Item Compendium, specifically at Runestaves. These little tools essentially expand your spell list to include whatever spell(s) the Runestaff is keyed to. Invaluable for the spontaneous caster.