Honestly, I feel like a slightly more bursty sage/sorc with slightly less survivability/less mobility and -significantly- less uptime with lethality. With marksman I feel like a merc who traded in his damage stripes for a couple tricks and no added survivability. As a sage it's not unrealistic to die 0-1 times a match and be DPSing literally the entire time. Your resource pool is simply massive in comparison and shield is easily the best ability in the game. A consequence of this is the most glorious uptime ever. As a merc your platforming role with arsenal is both simplistic and stronger then platforming with marksman. This is in no small part due to snipers horrible typing issues versus armor and possibly the most lackluster top tier talent in game; rapid fire. It's not uncommon to see a stimmed 6 second x3 rapid fire barely scrape 2k from a shield tech power tech if you are into masochism.
Frankly marskman almost feels like it needs an acid blade effect to apply on ambush. Either that or just replacing the 3 point alacrity talent in marskman to something not borderline useless like 30% armor reduction across the board. With lethality, I'm not sure why weakening blast is significantly worse then deathfield, the comparable sorc ability, but I can deal with that. On the other hand as one of the most dot heavy specs I'm not sure why we don't get a 1% health regen on dot crits. Yeah, it would be pretty epic, and put it on par or better then the marauder 100k end game healing per warzone, but we need something. For the sniper in general, I think giving us one of the get out of jail free cards in instant stealth isn't too much. In terms of group utility, we should've been given the sage ability rescue but that's a different discussion.
Edit: Don't even get me started on the supreme ease with which pre-mades with competent healers can dispel dots. 2 good healers can virtually nullify lethality spec across an entire match. Oh what's that you spent a third of your energy and 3 GCDs to prep a target for culling and sustain? Let me spend 1.8% of my energy bar and one GCD to remove any chance you have of killing/damaging me or other things. Did I mention that if you try to setup again I'll be ready in the next 4.5 seconds? It immediately and reactively negates roughly 7k damage. No idea why it exists.
Engineering is just bleh for anything other then afk door guarding/big numbers on voidstar.
I'm definitely not unhappy with the class, but for sacrificing the ability to spec into any other role I definitely feel marksman and lethality should at least be on par with arsenal merc/lightning sorc and madness hybrid/full madness sorc respectively.