For end-game / high level play, two things that are a given:
1) Your arcane power needs to be managed:
i) you want to use it to maximize dps
ii) you want some to be available for an important ability, when you need it
iii) you want it to replenish quickly, and need to consider your build and play-style with respect to this
2) A mix of Single Target, AE dps, and defensive abilities are required
AE seems pretty clear.. some runed signature abilities.. blizzard.. meteor.. wave of force.. explosive blast.
What are the top single-target abilities ? there needs to be a degree of AP sustain, and it seems like we're stuck with Ray of Frost.
Perhaps magic misslie, combined with something that sucks more AP ?
2) I'm not so sure about this one. It was just jay's recommendation. In some cases I might be alright to have just single target abilities an no AOE, and sometimes you will do fine with only AOE abilities.
But in general yes, if you go with at least one single target ability, one AOE and one defensive, you probably will do fine.
Well, I'll probably be going for only an AoE ability, + perhaps magic missile. At least to start with. The AoE abilities of the wizard do quite enough single target dps, I feel, and you only have AP for one spell at a time. I'd rather take an extra defensive ability than have one skill slot wasted at all times (either the aoe or st spell).
Although another thing to consider is the rune in ray of frost that makes it deal damage in an area around you. If the area is big enough (say the range of a frost nova or so), you could get a nova-like AoE and a single target spell in one
Well, if you can root the enemy, then Energy Twister/Wicked Wind is sort of a single target. Other than that, there is Ray of Frost, Magic Missile and Arcane Torrent (not Death Blossom). The Arcon also has a single target skill.
The thing is that there seem to be cheaper and/or more damaging AoEs that would work just as well for pinpointing a single target, for example: Spectral Blade instead of Magic Missile or Meteor instead of Arcane Torrent.