This is a pretty welcome idea and I applaud any efforts put towards fixing Character Building in D:OS2 (something I'm having a harder and harder time dedicating myself to) so I'll try to throw my two cents in.
On the topic of Ability Capstones:
If we take Summoning as an example, 10-Point capstones should be an alteration to existing mechanics and the central aspect of that Ability (In Summoning's case, making their central summon bigger and better), so I would try and move past just being thematic and try to tie these capstones closer to their sources in a way that both makes them desirable and significantly alters or empowers the way you play that character.
Here's some examples:
Pyro 10: Your spells and attacks automatically Critically Hit against foes that are Burning or are in Fire.
This drastically increases damage, Pyro's main focus, in a conditional way that plays off of Pyro's terrain generation and key status; and does so in a way that opens up further synergy with other Critical-oriented playstyles.
Scndrl 10: Whenever you score a killing blow, you become Invisible for 1 turn. Damage dealt while Invisible is increased by 40%.
This is tightly bound to Scoundrel's high single-target burst damage and mobility, further promoting these aspects by allowing the user to be rewarded for their investment with increased mobility, safety, and damage potential.
On the topic of your Attribute Changes:
Your benefits are too small, realize that a player will naturally only benefit from 25~ (60~ on an optimized Lone Wolf, but remember that this is its own issue, I would focus on non-LW balance first) Attribute Points by endgame. Don't be afraid to give players a little more bang for their buck (+1% Dodge, +2% Crit, etc).
I would also move the Armor-based benefits solely to Con, providing +2% (at least) to both for each point invested in it; and I say this for a variety of reasons (lopsided armor already being a player weakness, CON needing the love, etc)
