Agree with bpat. While Mindslayers can be plenty powerful, they are not very fun compared to other classes. I'd suggest these changes, which include some of bpat's:
Tree access:
1. Augmented Mobility is unlocked and doesn't require level 10. Also, reduce the psi cost of Mindhook and Quick as Thought slightly as they'd be a bit excessive for low level mindslayers.
2. Shield Offense, Two-Handed Maiming, and Dual Techniques are available locked at 1.0, similar to Arcane Blade.
Projection:
1. Make aura activation (and deactivation) instant. This would better parallel shields and make them much less annoying to use. (However, see 5. below.)
2. Don't deactivate auras on hitting 0 psi. Right now, this is mostly a trap for inexperienced players.
3. Remove aura psi cost on damage. It's rarely relevant and doesn't serve a balance purpose.
4. I don't think that replacing the psi cost is strictly necessary, but a better alternative would be that each sustained aura reduces psi regeneration by .15 or so (without extra psi regen, that's .20 => .05 with one, and .20 => -.10 with two). Alternately, sustained auras could provide a negative healmod for psi (affecting all methods of regaining it).
5. An alternative psi cost mechanic for auras could instead make them work like Deflection. Psi lost to keeping auras active builds up their charge until it hits a cap based on talent level. Dealing damage expends charge, and either the minimum psi check is replaced with a minimum charge check, or the effects scale with charge.
This is a desirable change if making aura deactivation instant! Otherwise, it will be possible to activate two auras, spike them, activate a third, activate Projection Mastery, and repeat for a total of six instantly spiked auras of damage.
Psi-fighting:
1. To account for more dual/shield mindslayer capability, make Telekinetic Smash extend to your offhand if present. If you have Conduit active, the damage is divided evenly between your attacks.
2. Make Conduit simpler: it just suppresses the damage of active auras and applies it to your TK weapon instead. No interaction with your ability to activate/deactivate aura talents.
3. Possibly, make Frenzied Psi-fighting a psi-draining sustain instead (a la Momentum).
Focus:
1. Remove the repeated Mindlash cost. It's irritating, hard to remember, blocks zoning, etc.
2. Improve Pyrokinesis slightly. Perhaps 15/15 psi and cooldown instead of 20/19?
3. Move Reach into Finer Energy Manipulations, and add a new lightning-based Focus talent, keeping up tree symmetry. Example:
Brainstorm
Use mode: Activated
Psi cost: 40
Range: melee/personal
Cooldown: 30
Travel speed: instantaneous
Usage speed: 1 turn
Is: a mind power
Description: Bridge the gap between minds with a spark of inspiration. Each turn, a bolt of lightning leaps from you to a random enemy within [low talent based range] for [low mindpower based damage] lightning damage. Anyone damaged by the bolt may be dazed ([~10-20 Cunning-based %] chance) for [1-3 talent based] turns. The brainstorm will only target each enemy once, but they may be hit by bolts aimed at others.
The damage increases with your Mindpower, and the chance to daze increases with your Cunning.
(Gem/mindstar bonus disclaimer)
4. Buff Focused Channeling somewhat, and make it more explicit what parts of aura and shield effectiveness will be increased (display the increase in the description).
Finer Energy Manipulations:
1. Remove Perfect Control - it's completely underwhelming/uninteresting. Replace it with Reach, as above.
2. Make Reach depend only on talent level. Basing it on gem/mindstar tier is unnecessary.
3. Get rid of the "reduced benefit from Reach" complexity by making Reach only affect energy manipulation talents (Projection, Focus, Grip, and possibly Voracity). Preferably, increase their range by squares rather than by percent to make the benefits clearer.
4. Scale Reshape Weapon and Reshape Armour off of talent level only, and change the bonus to a percent.
5. Not a huge difference, but I love the idea of making those two talents increase the ego modifier (say, by .05 per talent level) of psionic infused items. This would make them a better choice across the board for Mindslayers, which would be nice and flavorful.
6. Remove Matter is Energy - Mindslayers should get their psi from getting hit or from hitting. Replace it with a new capstone talent, Reshape Being:
Reshape Being
Use mode: Activated
Psi cost: 0
Range: melee/personal
Cooldown: 1
Travel speed: instantaneous
Usage speed: 1 turn
Is: a mind power
Description: Manipulate forces on the molecular level to realign, rebalance, and recalibrate a target being (or yourself). [...]
Permanent buffs are cool, and ones you can use on
escorts are even cooler. I've left the effect open here because there's a lot of room as to what 'recalibration' actually means. But when I think 'more perfect body', that might include: poison/disease/bleed resist, increased physical stats, increased HP, increased saves, crit shrug off, increased resists / cap, movement speed. When I think 'more perfect mind', that could be expanded into: mindpower, luck, confusion/stun resist, psi regen. Implementation-wise, this should probably gift a matching talent level of a passive talent that provides these effects.