I'm totally missing the Beguiler/warlock combo? They stack almost everything or make you choose to do one thing or another. You can't cast a spell, and use eldritch blast so one is a waste. Both have the same saves so no benefits there. Both get the same hit die so no benefit there. The beguiler gets nice skill points so that's nice. The warlock gets medium BAB so that helps. But the warlock doesn't benefit from metamagic feats like the beguiler does and the beguiler doens't benefit from ability focus feats like the warlock needs so you have to really decide which class you want to focus on and just run with it which means the other gets no love so just drop it as its doing very little for you anyway.
Beguiler benefits: Overcome SR at 20th level as a caster. This is the best thing about this class. d6 instead of d4s. Casts as a sorcerer from a spell list. Can wear light armor no spell casting penalty. 6+int for skills. basically skills as rogue
Nuetral things: Typical low BAB. Gets still spell and silent spell for free. Trapfinding. Most spells are Controller spells
Negatives: Must be in melee combat and succeed at feint or have opponent lose dex bonus to overcome SR and gain this ability. Must wait till 20th level to gain this ability. For nearly all that's worthless and even epic is still not a great boon as you usually have a 50% chance to beat it (most critters SR isn't so out of reach its impossible to beat, even our 15th level wizard could beat the SR of a CR 25 Demigod, just barely though)
So if you want a support character that has to be in the front lines every fight this is an option. I'd think Bard would be better though as at least then you don't have to slog through melee to do basically the same stuff.
And for you Warlock fans you really need to check out Supernatural Transformation in Savage Species. Its a Must Have feat for the Warlock.
Our DM had a Warlock/Monk Combo that was pretty awesome. That kobold always gave us trouble. And you don't need to wear armor.