If you want to tank, then first off you need to be getting all the AC you can. Best AC on armor, best AC on augs, and you will want to load up on HDEX. You want to get the highest AC shield you can use and put in the highest AC aug you can fit into the shield.
Don't get hung up on procs to hold aggro. You are much better off with lifetap procs. If you are remember your ABCs (always be casting) you won't have a problem holding aggro with your DD spells.
A shield is not suddenly going to allow you tank something you can't tank now. Equipping a shield does provide some benefits: 1) You swing less because you only use one weapon. This is helpful on mobs with high riposte rates. (2HB also works in this case) 2) Minor benefit from the shield block AA. (We need more tiers of the AA) 3) AC in a shield is allowed to go over the cap and provides more benefit then the AC in any other slot and helps to smooth out the damage spikes.
Downside of using a shield is that you lose 30% of your DPS and fights take longer so you have more opportunities to die.
Quad lifetaps are the way to go, plus the heal proc on the pet, and a J5 merc and you can handle almost all trash mobs and some named.
If you are fanatical about lifetap procs, then you know you can get a 1hb weapon called a snowball in Velious that can go in a ranged slot and hold a sympathetic lifetap proc aug. Makes me wonder if it would be better to have a sympathetic lifetap aug in the shield versus an AC aug.
-Z-
