I have a brand new Dobyns D684cb and Lew's TProG, it's a beaut. I have #10 Invizx on it, use it for squarebills and jerkbaits. I took it out for the first time yesterday, and I'm having a hard time getting the brakes right. Is there a chance that some of my issues lie in the diameter of the line? I got about as many birds-nests yesterday as I have all last season, and I just had to peel about half of it off. Want to know if that is a possible issue before I respool on 60 some yards of line. 

Well, that is pretty thin line, about 8# diameter. But shouldn't be impossible, I have used 8# on baitcasters for jerkbaits quite a few times. 

I would say it has more to do with the reel being new to you and not set up properly yet. 

Your brakes/spool tension  aren't set right or arent working .That line is very manageable.

It could be something with the reel too. A buddy has a Lews Tournament MB that will backlash with 40# braid spooled on it without applying much casting force and brakes and tension knob tightened down more than anyone would ever need. I have heard of this happening to others with the same reel. Could also be that the reel was overfilled with line. It can only be so many things.

The reel is overspooled

There is some mechanical issue with the reel

The breaks/tension knob aren't set correctly

Maybe spray some KVD line and lure on it to help.

From my experience Lews are pretty finicky. I had a Team Lite with 14 lb. Sniper (same diameter as 12 lb. Invizx) and it liked to backlash/overrun. I have a Chronarch Ci4 for jerkbaits that's spooled up with 8 lb. Sniper and it never backlashes. 

Casting issues are almost never the line, especially when dealing with very standard brands and sizes. I use everything from 8# InvisX up to 20# Toray on most all my baitcasters with no issues. Look at the rod, the reel and the baits. Good casting is accomplished with the proper combination of those three things. The line is just along for the ride.

-T9