Looking at this handbook (2010), (Be advised that he uses an unusual colour scheme, for people used to modern handbooks.) we can see some general patterns:

At the end of the day, you'll be looking for ways to bypass it. The two power that you should have, therefore, are Crystal Shard and Amethyst Burst. Nice, low-level powers that can be augmented well. Crystal Shard is a ranged touch attack (with all the ways that that can be cheesed). And Amethyst Burst is nice as an AoE.

The general pattern is: find the no-save, no-sr powers that are most compatible with your party, and take... them. Use the rest of your powers on doing Cool Stuff. Have your signature no-save, no-sr (probably ranged touch, though telekinetic thrust, with the right optimization can be cute), and have your backup no-sr, no-attack. In high epic, the game is silly. You should be focusing on "dirty tricks." Either doing the scry & die game with the opposition, or preventing insta-death teleports from happening to you.

You may want to focus on appropriate astral constructs. It's one of your signatures, and summoned monsters, when appropriately optimized, can be incredibly useful. Consider specializing in it with an appropriate PrC.

If you're really playing silly buggers, embrace taint (and the necessary hooks to ignore it), and grab Subverted Psion. That, combined with Thrallherd means that your evil army (all armed with appropriate magical devices of no-save no-sr powers), can just kinda swarm the badguys.

Pay especial attention here, where the optimizer breaks down some of the better choices:

Ranged Attack Roll Any power you select should preferably be a ranged touch attack. This means rays and the like. In this category, three powers stand out: Crystal Shard (Psion 1), Entangling Ectoplasm (Psion 1), and Crystalstorm (Psion 2). What makes these powers superb choices is that they all fill two other roles: they don’t allow a save (note that Crystalstorm does allow a save against its secondary Con damage effect, but not against its primary HP damage effect), all are instantaneous creation effects and are thus effective in Anti Magic/Null Psionics fields. Finally, none of them are subject to SR/PR.

Ranged attack roll: Crystalstorm (Psion 2), Disintegrate, Psionic (Psion 6)

Melee attack roll: Astral Construct (Shaper 1)

Targets Fortitude Save: Disintegrate, Psionic (Psion 6), Energy Wall (Psion 3)

Targets Reflex Save: Energy Wall (Psion 3), Amethyst Burst (Psion 2)

Targets Will Save: Time Hop (Psion 3)

Allows no Save: Crystalstorm (Psion 2)*

Not Subject to Spell Resistance or Power Resistance (SR/PR): Crystalstorm (Psion 2), Energy Wall (Psion 3), Amethyst Burst (Psion 2)

Area of Effect (particularly for fighting Swarms): Energy Wall (Psion 3), Astral Construct (Shaper 1)**, Amethyst Burst (Psion 2)

Force Effect (for fighting Incorporeal/Ethereal creatures): Amethyst Burst (Psion 2), Astral Construct (Shaper 1)**

Effective against Anti Magic Field/Null Psionics Field: Crystalstorm (Psion 2), Amethyst Burst (Psion 2)

Effective against Globe of Invulnerability: Disintegrate, Psionic (Psion 6)

Creating epic psi powers causes sanity loss, but given that they work like normal peic powers, look around for an epic spellcasting guide and plagiarize. Considering that you'll certainly have thrallherd and/or appropriate leadership chains, you'll have plenty of assistance.

Beyond this, given that you're in a stupid-optimization game, consider:

• Psionic Tricks handbook

There are a number of infinite action tricks there. I am especially amused by the save state trick. I would also ask to become a erudite with spell to power. Cause why limit yourself to only psionic tricks?

Based on the alternative class features thread, here are your options:

Rogue

• Antiquarian – +Wis to Appraise for divine items, can attempt to identify divine items
• Changeling Rogue – 10+Int skills/level, one Knowledge skill of choice as class skill, gain Social Intuition (several special features with social skills)
• Drow Rogue – Poison Use
• Mimic – Disguise self

Scout (none)

So only one that you missed, but it’s a really good one. Anyway, rogue/scout seems like a kind of poor multiclass to me; they overlap on a lot of things and their primary differences don’t synergize very well (rogue wants to flank, scout wants to move).

With the build I'm going for the Drow Rogue looks the most viable but really poison use appears to be more trouble than it's worth (especially with the cost of decent poisons...)

Poison Use is almost useless; if you want to specialize in poison, you really want the Master of Poisons feat from Drow of the Underdark, which gives you Poison Use and the ability to poison a weapon as a Swift action.

That said, poisons can be worthwhile, and better you can make decent use of poisons without investing heavily in them. Having Poison Use rather than Master of Poisons is mediocre, but Craft (poisonmaking) can generate substantial savings on poisons (prices as low as ⅙ the base cost). Tossing a few points in Craft (poisonmaking), carefully selecting cost-effective poisons, and having Poison Use can give you a fairly potent low-level option.

For more about making the most of poison, check out Arsenic and Old Lace.