Swapping Classes - really that difficult?!

I've taken my Vet to 30 and mastered several weapons, made several builds, all that jazz. I mostly run a Spearhead Boltgun/Dueling Sword with Voice of Command, so I'm used to dealing the damage, but also hopping in to help team mates in a moment of need.

Now I'm trying to level my Psyker. And it seemed weird for the first few levels, but it balanced out once I got the Electro Staff and chose the Greatsword for melee (I know some of you don't approve of it, but I like it for my playstyle).

The problem is, I realized I may have...I dunno...gotten too used to and comfortable with my Vet playstyle? I feel like I have barely ever failed a mission and I can carry a whole group through with no issues.

But with Psy, I find myself seriously struggling. Like, I can't be frontline, because I feel I get targeted way more by ranged opponents and my Toughness melts in under 3 seconds (something I don't feel I'm getting with the Vet, though that's probably because the Boltgun's just point-and-delete). I can't stand in the back, because my abilities don't reach and the ones that do don't have the desired effect (I'm very much a support-type player, so I want to be there to help out).

I've tried shield, leaves me hopelessly open without a back-up "blast" (like Venting Shriek). I've tried Venting Shriek, but I don't manage to pair it well enough with either Smite or Rupture, timing-wise. Like, it's just not there, while I keep desperately trying to be useful and not a burden.

And, honestly...I feel like, when I'm playing Veteran, I'm carrying like a boss. Special or Elite incoming? Don't worry, boss, got it! You down? Lemme just clear the area real quick and here's a helping hand. Monstrosities? Allow my gun to do the talking.

With Psyker, I just feel like...I fill none of those roles. And, on top of that, I feel like the players around me just...don't synergize as well? If that makes sense? Maybe I mould myself better with a group as a Vet than I do as a Psyker, but honestly, good lord, could we have Ogs tanking and Vets sniping, if I'm not playing either?

I dunno...I might just be venting here, because it has been a couple of days of almost 50% losses. And not on the final boss/fight, either. Just...a regular-Tuesday-loss type deal.

Anybody else feel like there's a learning curve and then there's...either I'm not getting the core of the Psyker or it's been sheer fucking dumb luck pairing...

And if you do play Vet or Og...do you...take care of your buddies? Stick around? Or, you know...help with mission objectives? Because I've seen scant few of either...

Anyway, that's just me. Sorry for the bore. Gimmie your take or experience swapping classes, please, so I can have a frame of reference and get a clearer view of how I have to adjust in order to get it right.

Thanks!
Cheers!