305d6 magical damage is a big number to throw around. That's 305-1830 damage. Yes, it's an incredibly difficult spell to develop, and it's costly... but it's also amazing.
Just one point....just one.
On good or evil aligned toons, a smiter can hit that with almost no problem. Take maybe 33 smiter levels and 7 WM lvls and all the great smite feats you can fit, and you've got an increased threat range and multiplier so any crit has at least 3 rolls for damage, which combined with the smite of between 250-330 damage depending on great smite feats taken makes one MASSIVE hit. The x3 multiplier would take that to 900 odd damage. With x4 that would be 1200, and with x5 (scythe, as you all know) it would be about 1500.
I heard from Daccid that he tested a smiter in his own little training-mod-thing and he managed to get a smite-crit of 2500 damage.
Granted, smite can miss...but you get three shots for free every day. The 305d6 magical damage would cost you big-time, and when you're talking about such large numbers, the average resistances of 5/- (magical) and 50/+20 (epic warding) don't make much difference. Well epic warding would. For the first one.