Replies first:
- Force of Will, Holy Reach, Surge of Light, Searing Light: Holy damage talents. They should be avoided if you're serious about either healing or damaging, but they make an excellent choice for some bg whoring or 5-man fun for the bored holy raider, especially if they start getting the good caster drops that the main casters don't need. Holy Reach is semi-useful for a raiding CoH priest, but that's it for raiding.
- Lightwell: Pretty much useless. Whether going IDS or CoH, there's better places to put it. The most use it has is throwing it near a couple locks on fights where AoE is predictable. In other words, not worth the talent.
- Improved Inner Fire: PvP only, and a waste of points even there. Take an undergeared (honor only) priest, 1439 armor with gear + base agility. Inner Fire brings that up to 3019, or 22.24% mitigation. Three points in IIF bring this up to 3493, or 24.86%. That's best-case - the %reduction goes down as the priest gets S3 gear because of the way armor scales (more around 2.2% with most of the best gear). Three talent points for an extra ~2.62% mitigation? I don't think so, there's better places to spend those points on.
- Martyrdom: Good for PvP, bad everywhere else. It does provide extra protection beyond shield, though, because a shield can be broken through (painfully easily at 70).
- Improved Mind Blast: Staple of every raiding shadow priest. Getting 4/5 post-Kara and 5/5 with T6 means noticeable increases in your DPS, but this is one of the talents that's most up tot he individual. Best place to test it is respec, have no points in IMB, and go at Dr. Boom until you run oom. Then keep putting points into it IMB one at a time, mana up, and try again. Stick with the number that seems to fit best for you (generally 1/5 or 4/5). Also taken 2/5 by arena spriests just to get deeper in the tree.
My own additions:
- Absolution and Healing Prayers: Unless your build somehow prevents you from getting it, it's better to spend points in Mental Agility instead of either of these two.
- Silent Resolve: Situational. The dispel protection is useful for PvP, but at a large talent cost. The threat reduction becomes mostly useless by the time you're in Outland (though can be useful in PuGs), and in raids it does little more than determine which healer dies first during a wipe.
- Shadow Resilience: Waste of talent points on par with Improved Fade.
And general rules that some people violate (though admittedly some people have fun doing the following, but it's generally a bad idea):
- 23+ points in Disc: Not for serious PvE. Goofing off with friends, smitespec, or soloing sure, but not in heroics and certainly not in raids.
- Holy/Shadow: No. Don't do it. Pick one, stick with it. Shadow heals fine until 70, and splitting the points means you're giving up solo ability for something you already do well. If you're determined to do both, go with a smite-based spec.
- Mind Flay + Non-shadow: NO. Flay is near-worthless without the huge %dmg increases deeper in the tree. A deep shadow's flay will be doing as much as 46% more damage than one that stops at Flay.