For melee, it is very obvious - new weapons = more dps. For me, when I go to a new expansion during leveling, that is the first thing I upgrade, then rest fills in. Tanks look for weapons and big armor increases. For casters, new spells = new dps. However, spells are so easily obtained be it just bought, or a drop to get a spell. And, T2 isn't much better than T1 IMO. Now, couple that with no level increase in so long. So, what do casters look for first in upgrading? What is their biggest bang for DPS increase? What are the must have items when looking to upgrade for a caster first when you get to a new expansion / set of gear / set of 5 levels?
Proc effects on weapons, unique proc effects on augs/items, clickies. Everything else is pretty much just stat padding. Examples of things that get me all "excited," if you know what i mean (with links!): Dark Shield of the Scholar Darkened Trakanon's Tooth Invested Tome of Obulous Augs that proc damage effects, like the Ancient Diamond Spell Charm or Bone Shards of Frozen Marrow Belts that proc damage effects, like the Runed Belt of Boromas Unique augments like the Sacred Prayer Shawl "Stat dump" items with silly amounts of Heroic Agility or AC, because I'm an addict. I like to solo and have a history of pulling lots of aggro, making survivability a priority, so items like this and this are useful to me. Foci upgrades. This is your first "big" item(s) and is generally a primary focus as it gives the most benefit. Basically anything that has a "meaningful" impact on DPS, which is mostly limited to proc effects and foci. Spell damage is so close to being a non-factor that I don't really get excited by a few extra points here and there. Plus, it's on everything, so whatever. Stats are not very impactful on casters, so we have to look for other avenues to squeeze some extra 1's and 0's into our end of the night DPS.
Focus effects of course. Spell damage, healing power, duration, range, mana cost, spell haste. The sorta blah factor is how standardized those are. In old days, each focus type came in a number of tiers. These days they are more or less the same. Only variance if your item is lower level. I.e. foci on Boreal start losing potency past lvl 100. But once you, say, got your T1 TBM group piece, there is really not much on group side of things except stats. I.e. T1 TBM Crypt-Hunter chanter wrist haspretty much same 55-75% spell damage focus as EoK T2 Selrach's. Still a real nice upgrade as those extra stats add to survivability, but if one wants a better focus, raiding is the only option (65-100% damage focus on TBM raid chanter wrist) Sure, I would be happy to replace my Deathseeker with Velazul's, but it would be a pretty much stat only upgrade for me. Unless new cap happens to be lvl 115...
