You smoked a full packer in under 9 hours from what I can tell. I personally usually take 12 to 18 hours, sometimes in the past even more.
Of the 5 pellet grills I own, the one that smokes the best , really starts to taper off in smoke production at about 275F, and for the most part the best smoke it produces is at about 225F. A couple other pellet grills I own start to really taper off with smoke production at about 250F.
My recommendation would be to run at about 225F to 250F on your next cook, 225F until the stall, then bump it up to 250F after that... and just wait it out. I also highly recommend getting some 100% Hickory pellets, they produce about the best smoke flavor of any pellet IMHO. I do run 100% Mesquite now and then, or mix it with 100% Hickory sometimes too, but 100% Mesquite is a bit tricky to find sometimes, and I still feel 100% Hickory will give you the most flavor, regardless of the availability of Mesquite. You might want to add a pan of water off to the side ( near the hottest part of the grill, so it'll actually get the water near boiling to produce some steam. Some say the moisture will help smoke 'stick' to the food, I don't know for sure if it does, but I do personally like the way my brisket turns out with a bit of humidity added into the grill. )
Pellet grills do give a more subtle smoke flavor than many stick burners do, however you should be able to produce some very good tasting brisket on a pellet grill.
A brisket I cooked this weekend