Help with Sorc on Terror's Domain

[QuackinKraken]

I have a level 28 Sorc, with decent gear, but I cannot seem to clear Terror's Domain. I cannotOn Normal. I know, it is depressing. I am not sure if I have a small brain, or if I am missing something vital.
I have farmed LT a lot for gear, as well as Hell 13-15 for exp.

Here is a list of stats you can look at to see if my small brain overlooked something I need

My important stats
My AC is at 90
Magic is at 227
Resists are as follows:

Using Naj's:
Magic - 0%
Fire - 55%
Lightning - 19%
Cold - 50%

Using Cathan staff with 3 piece set bonus:
Magic - 30%
Fire - 75%
Lightning - 49%
Cold - 75%

Obviously there is a big difference between these two, but until 30 minutes ago, I did not have the Cathan staff. I haven't attempted with that staff yet.
Is it worth to lose the 28 bonus to magic for the resistances? Do the resistances make that much of a difference?

My Gear is as follows:

Cathan's Mask: AC is 36 with set bonus, Cold res, 24 mana.
Maidens Broach: 5 to all, Fire res, Mana regen, Mana leech.
Light Plate: 40 base AC, Fire Res and 19 to Magic.
Ring: hit%, Lightning res, +1 to all, 8 to magic.
Cathan's Seal: life leech, -2 damage from enemies
Belt : 7 AC, Cold res, Life regen, 10 to magic.

Staves:
Naj's: 28 to magic and 5 to dex.
Cathans: Spell LV +1, 62% undead, +4 Holt bolt.

My spells w/o items to increase spell level
Chain Lightning is at 10,
Fireball is at 10,
Ice Blast is at 9 (For the occasional demons that are immune to Lightning and Fire)
Guardian is at 8. (Still haven't done Chamber of Bone)
Golem is at 7 (Haven't done Horazon's Sanctum)
Teleport is at 2 (I have the Naj staff, I mainly use that for my teleports.)

I have chain lightning on left click, teleport on f1, fireball on f2, ice blast on f3, elemental drain on f4, and then buffs and the like on f5-f7 (Tp, mana shield, ect)

I do not think my hotkeys are set up bad, nor that my gear is terrible. I am pretty sure my character is adequately geared to finish the game on normal, but my mana just gets absolutely melted.
I am not sure what else to do.

My main questions are:

Do the resistances make such a massive difference that I need to only use the newly found Cathan staff?
Am I missing any stat vital to being able to clear, and eventually farm Diablo for gear/exp?
Is there a piece of gear I am using that I need to upgrade as soon as possible?
If I need better gear/spell lvls, is there a better way that LT for gear and mages after for books?
Or is my equipment and spell levels fine, and it is just user error?

Any advice would be greatly appreciated.

[D1sfigur3d]

Study this:

viewtopic.php?f=3&t=2298

[QuackinKraken]

That is what I read when I first started playing, that is why I knew to invest most all stats into magic, and to not complete Horizons sanctum or Chamber of Bone. I just cannot get anything killed in Terrors Domain at the moment.

[D1sfigur3d]

That is what I read when I first started playing, that is why I knew to invest most all stats into magic, and to not complete Horizons sanctum or Chamber of Bone. I just cannot get anything killed in Terrors Domain at the moment.

I don’t actually understand the trouble
Do u have full monster description enabled in the game settings? If not turn it on so u will be able to see a monsters immunities. Probably u r just not using right spells against specific enemies

[QuackinKraken]

That is what I read when I first started playing, that is why I knew to invest most all stats into magic, and to not complete Horizons sanctum or Chamber of Bone. I just cannot get anything killed in Terrors Domain at the moment.

I don’t actually understand the trouble
Do u have full monster description enabled in the game settings? If not turn it on so u will be able to see a monsters immunities. Probably u r just not using right spells against specific enemies

I ended up switching to the new staff that gave me almost max resistances and i stopped getting dropped so fast lol