Here's something interesting I guess, although it's mostly academic unless you plan on doing a solo run at some point. Damage or healing dealt directly correlates to experience gained. I was curious if there was a difference between hits, crits and grazes in terms of experience (there is, but only in the way that the damage is different), or if experience was simply based more off of the number of uses.
It also seems like any time you use a melee skill that is associated with a support skill, the support skill also raises somewhat. I'm not entirely sure what causes the difference, but sometimes it seems like a skill that say uses Athletics will raise Athletics equal to the damage dealth with that skill, but it seems to either be inconsistent, or I'm not paying attention. I'm also not quite sure what affects Lore's rate of progression either. It's abysmally slow outside of trainers, even with the talents that give the group a bonus.
Also, damage over time effects add experience per tick too, so if you had Magefire (or Bleed) on a cone spell and you hit a bunch of enemies with it and ran away, you'd gain a bunch of experience until the dots expire.
Buffs only seem to add experience when you get hit, or hit with a weapon. Maybe there's a passive effect that kicks in over an extended period, offering you a small gain just for casting the buff and having it on during combat, but it seems like to get any real gains, it has to actually be taken advantage of.
You can really abuse this in Act 1 to gain 1-2 more levels on your main character, if you plan on delving into the Leadership tree, especially if you're a tank, and you don't plan on using Barik or Verse after as soon as you can replace them. You can use something like a low recovery, lower damage weapon, buff yourself and just take hits while healing and slowly killing the enemies. You'll raise Dodge, Parry, Illusion, and Control Life pretty easily.
The skill leveling is about what you'd expect from a TES game as some assumed.
