Scoundrels are very, and I mean, VERY powerful, IF used properly. Now the things you need is high speed, invis pots, and a lvl 5 crafter/blacksmith in party. Aiming at endgame, you only need about 10-11 dex (that about 17-18 with equipment), everything else goes into speed and only speed, and you'll need some equipment to get a bit constitution for max AP, but that goes only from equipment, not from boosting base stat! Seeing you have 12 perception you're pretty much screwed anyway, since you can't respec companions (well you can one of them, but that's not wolfgraff).
To make your scoundrel useful, you need 2 crafted daggers with speed bonuses (IIRC at 11+ lvl they'll give you +2 speed), of course put essences/poison on them, tormented souls (again IIRC at 11+ lvl it goes to +2 dex/str) and whetstone them. You need the super lucky magic rabbit paw amulet which is the best amulet in the game anyway (lucky magic paw + stardust, then + thread, then + bowstring). All other gear should be with as much +speed (and those few +con) as possible, if cant get speed get +movement at least, or +turn AP. Your speed should ALWAYS be the highest uneven number possible. Stun immunity on a ring is generally also a must have, as well as NIN on boots so you won't slip on that ice your mages just created with ice shards.
You also need DW 5 as soon as possible, it's easy as at levels 10+ you start getting belts with +1 DW, so 4 base is enough.
The tactic with that gear is - bless/oath on the rogue, stun/freeze/blind whatever would do too instead of bless, knockdown is even better with guerilla (with guerilla its best your earthmage buffs the rogue and does earthquake, then the rogue does the rest). Melee power stance. Then run around and destroy enemies until you have 1-2 AP (the attack with DW 5 costs 3 AP), the Adrenaline, then repeat, then invis potion at 2 ap or walk in shados which costs 1 ap more (3 ap).
I've played through vanilla 2 times, and numerous times through EE, and i'll say that scoundrel is one of the most imba chars, if done right. It needs some buffs/debuffs and support from party, but then the damage output is insane. The DW warrior is more straightforward and easy to play, however has less potential power, as well as ranger.
Oh, and if you cant get close to pwn those mobs, make the scoundrel a grenade-thrower too. About 10-12 grenades per turn at end game (with adrenaline) is just insane. If not, you can always cast 5-6 master-level scrolls, which is insane also.