God, Swordmages are terrible Defenders! Or at least, the one in my game is.
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It's an Eberron game, with the following party make-up (1st level):

Half-Elf Thaneborne Barbarian (me)
Warforged Wrath (the striker-y one) Invoker
Warforged Warding Swordmage (yes, with improved Warding)
Changeling Psionic
Kalashtar Monk
Human Artificer

So he's the only Defender and I'm the only Striker. Even with the boatload of Controllers here, the Swordmage has almost always gone down while I'm teaming with him - and I soon follow. Why? Because when he marks things he gets pounded into the ground. Oh, I love his Warding (Ward + THP = ) but it only works once per round (Immediate Action, y'know). This means he usually has to pick between Warding me or the Monk (for baddies with burst effects) - not a good choice.

I'd love to have a Fighter in the party who can at least deck the baddie if he takes a swing at me - or a Warden who can suck up however many baddies he wants. Hell, a Paladin would be better - at least he can throw out some Lay on Hands