Originally Posted by
Carpone
Limited feats, limited enhancement points and 3-day cooldown on swapping spells.
If you go the insta-kill route, you'll want great spell pen (at least the enhancements) and perhaps the appropriate focus feats (if you don't take the spell pen feats). If you go the DPS route, you'll want evocation focus feats and both elemental and energy enhancements.
If you want an arcane caster that can do both insta-kill and good DPS at the appropriate time, then play a wizard. They have the feats and spell-memorization mechanics to support that playstyle.