If you're just mobbing in niff, you don't need max VIT. Steel Body gives you more than enough defense on its own. Some Vit is good just so you can have more than baseline HP, but it should be a dump stat, not a main stat.
Since you're mobbing in niff, you will want a Bapho-carded weapon (if you're killing the mobs one-by-one, you really should be on a different map).
Since your ASPD gets slaughtered by Steel Body, you should use a DDBS weapon, and also have enough AGI so that you have as close to 190 aspd as possible (get 190 if you can, though I can't remember if that's possible without adding a third dopple card to your weapon - obviously, don't forget to use a speed pot). Another benefit of the high AGI is that you will have a fair amount of flee which can help you stay alive when Steel Body goes down. This can be aided further by swapping out with flee gear when Steel Body goes down until you get it back up. Obviously, this won't help you much if you stand in the middle of a huge mob, but if you fwing away when Steel Body goes down, then you should be able to ignore a couple of monsters that might try to bug you while you recast everything. You should also get Dodge to level 10 for the added flee, as well.
Fist/Claw weapons are faster than mace/club types, so your best bet would be a 4-slotted Barrage Fist (I think that's the name - it's the newer neutral-property Fist weapon that makes Waghnaks totally obsolete by comparison). If you can't afford (or find) one of those, then it's sort of a toss-up between Waghnaks and Maces. The former will be faster but weaker, while the latter will be slower but stronger. The damage difference between the two isn't as huge as the speed difference, though, so it's probably best to use a Waghnak.
Get the highest strength break-point you can afford after getting your ASPD to where it needs to be.
Get enough DEX so your cast time doesn't totally blow. Either that or have cast-reduction gear swaps for when you need to recast your Steel Body.
You won't need INT or LUK. What little MP you wind up using on recasting your buffs can be replenished with a little GJ.
While you only need to get RTB up to level 5 in order to get Steel Body, I highly recommend you max it out so that it triggers as infrequently as possible. Every time RTB triggers, you won't splash damage on the rest of the mob, so it cuts your mobbing efficiency down. Don't even bother using the other combo skills. It's a waste of time and MP considering most of them can't splash their damage, making that Bapho card useless.
I can't remember if there is splash damage when you crit or not. I know that if there is the splashed damage won't actually be critical, but I can't remember if there's any splash at all when you crit. If there is splashing when you crit, then you should also get Fury and use it. When you crit, you don't RTB, and so between higher crit and lower chance to RTB from having it maxed out, you will see fewer interruptions to your damage-splashing. If crits don't splash at all, though, ignore this skill. It will only hurt your efficiency.
You will need Eddga Shoes so that you can actually move while being mobbed. Your movement speed will be so ridiculously slow that you will pretty much find yourself frozen in place if you don't have these. They're standard Nif gear anyway, though, so you probably already have a pair.
I think that about covers it.
