I am a Rogue and i have 6 souls. In raids i mostly play DPS as my main soul. So far the best DPS builds for example "Ranger" 51 and Bloodstalker are dependend on Costreduction. Fervor is perfered. Without a doubt Bloodstalker is the best meele DPS spec for rogues. But at the same time without training you will end up doing bad DPS. By looking at the other classes they all have rotations and stuff. But the big difference is that they all can train their rotation on the dummy as lons as they want. Or until mana is gone. None of the Builds really need Fervor or stuff to practise a rotation.

Not having Fervot as warrior isnt causing any issues in your roation. The same goes for Mages and Clerics. Yes they will go oom faster but thats not the point i want to make.

For a Rogue to practise a good rotation for example a Bloodstalker rotation they need to have fervor in order to have the same flow of skills like in a raid. But be honest who has a Bard standing next to you in Sanctum or Meridian only doing fervor and being afk? Well at least not me.

So my suggestion is to simply implement NPC's that provide some buffs for example:

Bard NPC: Fervor, Motifs, Fanfares
Archon NPC: Archon Buffs

Maybe other have some more ideas than me but. At least for me its not easy to train a certain Spec at least as a rogue.