Is he suppose to be so bad? I'm playing on expert diff, I'm walking through a dwemer ruin with him as a follower, I'm taking out 2 spiders on one side of the room and when I finish them off, I look and see that J'zargo was killed by 1 little dwemer worker spider. I can't make it through a single room (that has a good bit of enemies) without him dying. I'm level 20, well equipped as a spellsword, and I can only protect him so much. I thought he would be good seeing he has a large magic arsenal and levels with you (and he's a badass Khajiit) but he dies constantly. Am I just better off with someone like Marcurio? J'zargo is just a hassle.

J'Zargo is my level 34 Mage's follower and he is really good. What annoys me is that from time to time, even just accidentally hitting him with a spell makes him call the guards and leave my service (even if we're in a Dwemer ruin, lol). But overall, he's a very good follower, despite being a snitch.

Once I was using Telekenisis in the Windhelm docks, and I was seeing if I could hit a bucket over the wall, I had to stop because it hit J'Zargo once and he called the guards. Stupid cat...

he's one of the best follower npc's at high lvls, like 70+'s
Since he's one of the few NPC's that continues to level up with the player, all the way to lvl 81.

His stats might not be good at lvl 20 though.

.

jzargo is a decent follower and he should be really good at your current level.He is the only follower that levels up to 81 with you.But yes Marcurio is actually way better than Jzargo because Jzargo only uses novice destruction spells even at level 81.But even so, he shouldnt be that bad as you mentioned.Are you on the latest patch?Before patch 1.7 there was a bug where followers would not level up with you.So if you got the follower at lvl 1, he would remain lvl 1 for the whole game unless you wabbajacked him.

This,

You can't expect a high level follower to be good at level 20.