Assault Swordmages are also about aggregate damage, not single target attack damage as partially stated above. Extra attacks add up, area damage adds up, non-standard action damage adds up.....
I have a paragon Earthsoul/Causticsoul Elemental Tempest Assault Swordmage and play him like a rescue ranger rather than a hold-the-line defender. I have elemental resists out the wazoo and can access more just by using my action point to get in an extra action. From sucking the Warlord out of the Gelatinous Cube's belly then teleporting out to attack the cube's marked buddy to Lightning Luring the aura-wielding Wraith away from the 5 HP Mage to Dimensional Vortexing the Brute's Crit from my companion to his own artillery/controller to jumping in to the enemy backfield and taking the BBEG Necromancer's worst in-stride while the rest of the team focus fires on his support is very useful and a lot of fun. But I don't have a bunch of 3[W] and 4[W] attacks.