| Time to deconstruct basic attack at least:
+7: +2 (level), +3 (longsword prof), +1 (enh), +1 (stat). So, that's still based on Str.
Let's look at powers.
Booming Blade is +9 vs AC. I'd expect the extra +2 is from stat bonus, so that points at Int.
Sword Burst (+6 vs Ref) has Implement instead of Weapon, so it loses the +3 longsword prof bonus. Again, points at Int.
Chilling Blow & Corrosive Ruin are also +9, as are Frost Backlash and Lingering Lightning; all-in-all, a persuasive case for Int being the primary attack stat for at least this particular Swordmage build. High Con is due to being a dwarf; looks like the character put 16 in each of Int and Con (and has put the level 4 +1 to two stats in 'em as well).
__________________
The Evil DM's Motto:
"I don't kill characters. A dead character can't suffer any more...." | 
And yet another word from our sponsors
