So far the only way for a mage to kill dangerous enemies (ie dragons) that I have found is Tensors. While this kind of works my attack bonus even with my strength buffed up to 30 and aid and bless running on me is incredibly bad (ie I cant reliably hit something with 34 AC like that Klauth).

Any ways to increase attack bonus beyond bringing a bard?

(Sorry if this is a repeat post by the way. Made one just like this, it was on the forum for a minute then wasnt anymore.)

Low attack bonus is the downside of being a wizard or sorcerer. There is the Eldritch Knight prestige class in NWN2, but it's not as good as it sounds given that NWN2 has some other amazing prestige classes for spellcasters.

My favorite approach to dealing with enemies who are impervious to my magic is use spells like Acid Sheath and Stoneskin. Stack enough damage retaliation spells and keep up enough damage reduction, and they'll kill themselves for you.

Looking up the retaliation spells, with a few of them active at once (assuming they can be) the damage sounds like it might start adding up pretty quick. I dont have any of them beyond elemental shield unfortunately :D.

Is there any way to defend against dispelling? As I could wreck him without him dispelling my buffs off of me. I get him down to well into the injured/badly injured health amounts and then he dispels me and I dont do anything after that.

Pick spell penetration feat also, use some spells like Acid sheath + Elemental shield defensivelly and ofensively, you can use http://nwn.wikia.com/wiki/Evard%27s_black_tentacles Evard's black tentacles

IF you need to go melee, then use Tenser's transformation or shapechange for the increased health Depends. In chap 3, i believe that you can purchase scrolls that allow you to stop time(tier 9 magic), so you can stop the time then recast your spells. What level your character is?

In hotu expansion, the "final boss" uses a lot of dispell also, he teleports you. Here is how i fought against him THERE ARE HOTU SPOILERS in this video https://www.youtube.com/watch?v=98j2JNmkc5I