A simple solution for Swashbucklers, Acrobats, and Assassins: add a conditional which doubles your crit range bonus if you have the relevant Imp Crit feat. E.g.:
- Knife Specialization: You gain a +1 Competence bonus to Critical Damage Multiplier with daggers and kukris. Daggers also gain a +1 Competence bonus to Critical Threat Range; if you have the Improved Critical:Piercing Weapons feat, this bonus becomes +2.
- Staff Specialization: You gain a +1 Competence bonus to Critical Damage Multiplier and Threat Range with Quarterstaves. If you have the Improved Critical:Bludgeoning Weapons feat, you gain an additional +1 bonus to threat range.
For Assassins, daggers & kukris maintain parity with each other. For Swashbucklers, the base weapon types maintain parity too, although some of the better
named weapons still lose out due to Imp Crit changes. For Acrobats, it's a bit more tricky: Sireth still loses DPS, but a bit less than it would otherwise; TF staves will actually gain DPS in LD (16-20/x3 vs 17-20/x3); other named staves are a mix.
Naturally, this presumes Turbine doesn't want all Swashbucklers to switch to rapiers or all Assassins to switch to kukris. If the imbalance between weapon types is
intentional, well, I can't help there, other than to say it's a
very bad idea, IMHO.
As for Celestial Champion, in order to compensate for the loss of Imp Crit stacking, I would make it a two-tier ability: "
Celestial Champion: +1/
+2 Critical Threat Range with all weapons (does not apply to handwraps or while in an animal form). When you critically hit with an attack, you gain a stack of Celestial Fervor. A stack of Celestial Fervor grants you +1 Enhancement Bonus to Doublestrike and Doubleshot chance. Stacks up to
5/10 times, with a duration of 6 seconds.[EDP cost:1 Ranks: 2]"