A classic blaster build is wizard 7/shadowdancer 3/frost mage 10/arcane scholar 10.
http://nwn2db.com/build/?206229 (Example build)
Its effective, and it contains some excellent goodies and RP potential. This can also be done with blood magus instead of frost mage.
Another one is Wizard 5/Frost Mage 10/Arcane Scholar 10/Palemaster 5.
This one is a little more tanky and does not feature Palemaster's arm, allowing you to not have to RP that. And it can be any neutral. Like before, you can insert blood magus instead of frost mage.
Finally:
http://nwn2db.com/build/?251926
This build is a HiPs DC wizard, who features DCs comparable to many high DC builds as well as HiPs. As the name might suggest!
For none wizard builds:
Druid 12/Hierophant 8/Hospitalier 10.
I haven't built this one, but it can lead to better DCs than a fully shifting druid if you pump full wisdom and take as much hospitalier as possible in the epic levels (then use its bonus feats for +wisdom). It makes a good blaster but its more DC oriented.
Warlock also makes for a good blaster.
http://nwn2db.com/build/?228310 This is a CHA-based DC warlock who is more CC than damage.
http://nwn2db.com/build/?128511 This is a CON-based warlock who does good damage and is very tanky as well.
Notes:
--If you'd like details on the none shifting druid or the wizard with 5 palemaster, PM me. I'm sure I could build it when I have time later.
--If you are deciding on your wizard opposing school, I would choose:
Enchantment: You lose greater heroism and dominate, those are really the only spells of significance.
OR
Divination: You lose a fair few RP-centric skills, but not many with mechanical significance.
--I would personally steer clear of sorcerer. Its not a bad class, but:
1) It loses out on many of the new spells, because its spell picks are so limited.
2) It gains from that ordeal 1 additional spell a day (specialized wizards cast 5/day, sorcerers cast 6/day).
3) Sorcerers do have spontaneous casting, but its not really that useful once you get to learn the ropes and develop a spellbook for every situation (or 99% of them) on your wizard. Which is fully doable, especially so with frost mage (though, FM isn't necessary for this).
4) INT is a better core stat than CHA unless you are shooting for divine shield. Even then, I consider HiPs far more effective, and wizard opens up HiPs far better than sorc does. You need to seriously gimp your sorc to get HiPs on it. It also turns you into a skill monkey, which is always fun.