So, I have been playing with mage for sometime now and I'd say I liked it for the most part except few things. Mages are really squishy at the beginning, I died a lot early in the game, it was like if Grissenda died then it's probably game over for me as well. I was using a battle mage build till my early 20s, with mainly Lightening Bolt and Disintegrate. After the Ark only I went with Summoner and I'd say I like Summoner build more. I really didn't face any major problems in SoH, I did died a couple of times at Plane of Fire but other then that, my mage was doing real good. Killing the Unweakened Undermother wasn't that big of a task either, I used the Corruptor staff and summoned an Iron Golem along with Grissenda.
Overall, I like mage a lot. Playing with them is a bit challenging but it does get better at later stages, leveling them is also much easier because of the exp. bonus you receive from the intellect trait points, they're pretty good with disabling traps as well.
If I'd have to improve one thing with mage, I would suggest for better skills management. Some of it's skills do take a lot of points. And I wish Arcanist provided some extra damage bonus instead of just reducing the mana usage.
Anyhow, here's my build:
And here's Grissenda, she's pretty good at her job:
Some tips: For Ark
[*] Mage with Lightening Bolt works good enough along with Tesla Rod. You should also have Mage Barrier on, when spiders hits you they get a hard shock and also get pushed back, so you don't have to worry much about running away from their explosions. For SoH
[*] I used a Summoner build at SoH, while progressing in the SoH I got Tomes of Lost Wisdom and also got Disintegrate I, which certainly helped at some situations.
[*] Carry potions of speed and greater potion of resist fire with you for Plane of Fire. Also carry fire resistant gear, I did a mistake and didn't had much fire protection except the potions. Luckily, David has placed greater ring of fire x2 in couple of chests there which really helped me. But I'd recommend carrying Dragoon Boots and Ring of Red Sorcerer with you.
[*] Carry Greater Potion of Resist Toxic for Sewer of Horrors, without them you may have trouble in activating all the levers.
[*] Staves to carry: Staff of Dead Kings for Mutant Rats, Magma Greatstaff for Animated Waste/Ice Elementals/White King, Tesla Rod for Skeleton Champions and Demilichs, Staff of Great Seas/First Winter for Fire Elementals/Greater Demon/Saradan/Lord of the Pit.
[*] Also carry Scroll: Circle of Restoration and large amounts of Elixir of Galade/Medipacks/Mana pots. Miscellaneous Tips
[*] Invest trait points in Agility, it gives +1 armor as well as increases damage with staves. After Intellect, Agility is the most important trait for the mage according to me.
[*] For companion Grissenda is the best, she can tank pretty well and you can just stay away from the mobs and hit them with spells/staves. However, I am yet to try Hirge, if you have a build for Hirge then please do suggest in the comments.
I would like to have feedback on my build, in case I can improve my build in any area. Let me know if you want to know anything else.