There used to be a formula, later down in the EQ expansions that actually gave you the trade offs between each stat so you could balance your gear accordingly.
The biggest problem when it comes to AC is the fact that you have to play it by ear.
For example, there are a lot of people that will tell you that AC in P99 is broken. Or that it doesn't work exactly like it should. Others will tell you that AC is awesome until you hit the hard cap, and then gives diminishing returns as you reach the soft cap. Or that there is no hard cap and there is only soft cap. A lot of speculation going on about this stuff, and more so here in the forums.
As far as your questions, from a paladin stand off :
1 -- They are good, and they are worthwhile. The degree how ever, varies in regards to where you exp, what you are fighting, and what your group is consisted off. If you pull non-casting, fast hitting mobs to a group without a slower, AC will help tremendously. If you are pulling Guk/Krup wizards around corners to your group, AC will not help you much against getting Ice Cometed.
2 -- Preferably look for both. AC/HP or AC/STA. The thing is, at this moment, there's no 'magical set on stone' number that you can follow. Someone might say "Well, you should only trade 1 AC per 5 HP on gear". The other might say "I disagree, you should only trade 2 AC per 5HP on gear". Truth be told, until you reach the hardcap on AC, then you should never neglect it. As far as to choosing gear pieces and comparing, again it comes with experience and factoring in other parameters. In your example, one will argue that 17ac + 30HP overshadows 22 raw AC mainly because resists aren't into the equation. And the biggest rule of Everquest is that "A distant lack of hit points is the number one reason of deaths in the game". So, your resists are lacking? Then your HitPoints 'become' your resists. (Although basically it's Level>Resists>Hit Point pool, but you get the point here). But in the other hand, if your AC is severely lacking, then 22 AC might come out on top in the long run against 17AC+30hp. Why? Because you will mitigate more damage, making it easier for your healer to keep you up, thus managing their mana pool better. For example, it won't do you any good if you have 3k HP at 60 and be absorbing damage like a chain or leather class.
3 -- Deepwater Greaves are currently BiS. The Breastplate is very good to have during your leveling, since it's a manaless heal. Statwise, Valorium breastplate is 'better' due to +STA (since neither has any resists, hit points are kind of desirable to have). The rest of the Deepwater set, I would advise you to get, and keep it. When you start being able to click them (46), then you will find a lot of perks. Helm is a clicky (non reagent, chest eats jaspers) heal. Arms allow you to manaless lull and save you a gem slot in your spell selection. Bracer can be used as a manaless pulling tool or even as a threat generating tool during fights (yet channeling a 7sec cast which is the duration iirc might prove challenging) that you have use if you run close to oom. Gloves again save you a gem slot and can be used as a pulling tool. Boots give you access to a spell you currently don't have. They are all useful imo. Would I rank them higher than the enchanted dwarven plate armor during leveling (for dwarves)? Probably not.
Velious will change a lot of that, you'll have a lot more gear choices, and most of them will be more clear cut and easier to pick the best piece amongst the ones you compare.
__________________
Lorraine Solamnus
Knight of Mithaniel
~=< Hated, Adored ; But never ignored >=~

|