Yo Chadddddddddddddddde!
It is my opinion, and shared by others I know, that leveling through the Epic levels IS a special grind unto itself. Call it the Epic Double Grind-Grind. Or, whatever. If you've done it once, then it was the best and easiest time of it. Every consecutive attempt at Leveling an Epic Character will get less and less interesting. Hopefully, for the Player, that would be off-set by more and greater opportunities for Role-play, thus one would completely forget about leveling, and to quote, one simply "enjoys the ride."
For example, let's just say a Player has 1 hour of game time every day (yes, that is not the average Player!). Grinding for XP in the Epic Levels, solo, is about 1,000 XP per hour. If you group up, you can hit 3,000 per hour in the right Area. Level 20 to 30 is 235,000 xp +/- ECL and XP penalty. So for a soloist, that is 235 days @ 1 hour a day, to grind through the Epic Levels (not counting more/less IG time per week, not counting visiting the Fugue...cause you know it will happen at least a few times).
I wonder how many Players coming to NWN2 and BGTSCC want to spent 2/3 of a year reaching one type of End Point in the Game, which isn't just Level 30, but instead actually experiencing IG all the content (mobs, Areas, Bosses, etc.). I'd say it is probably more likely 1 year commitment to Level a PC to 30 for the average Player who just plays a single toon. I'm just spit balling here.
So here is kinda the dilemma, which I think you're touching on directly, Chad 'ol boy: why spend so much time taking FOREVER to get to Level 30 when you can have much more immediate fun, and variety, but starting again on a Level 1 character and play with all those different buttons and options and such...and STILL CAN HAVE THE RP!
That's the think about BGTSCC: low through mid Levels are so much more gratifying because of sheer rapid progression, and you get pretty decent returns in terms of gear and such, and you often find a greater population of Players within your PC's level, than you do when in the Epics (because honestly, except for the Looters Club, what point is there to adventuring when at 28, 29 or 30?).
On a side note, I finally managed a Level 30 toon the other month, after not having any PC above 24 for about 5 years. I just couldn't see the point, until it had been so long since having full mechanical manifestation, it seemed tempting enough to actually "put in the work" to get there. I'm wasn't really satisfied though...except for the fact that I now have an uber pawning Character that can be the bad dude on the block (which is fun now and then). Funny enough, I mostly and still just RP with the toon!
A glaive-lock is super easy to play. I still think a pure blaster will still struggle (you'll need to multi-task the toon, else it will be a slow slog). What I'd challenge you with is doing Zan and mine's Single Class Heroes challenge! Take a Base Class to Level 30, no PrCs, no multiclassing. And THEN see how far you get, and if you think it still is enjoyable! Or, make an ECL +1-2 and 20% XP penalty toon. THAT will slow you down mate!!! lol.
BTW, overall, BGTSCC has an amazing range of awesomely build Areas, and I think we are all super spoiled in that more show up every month or two. It is really a moment to send you L.O.V.E. to the Devs and Scripters, publicly or privately, about how enjoyable they make this gaming experience (except for when they don't...yeah, you know who you are frenemie!!!).

The only thing that I think could make it better than we already have it is if already existing Areas had some fluctuation in CR and mob-type, now and again. Like, for example, taking the Cloakwood Mines, and just doubling the CR for a month or two. Then, after some IG experience and hopefully generated IG RP around the new "epic infestation of foes," the CR would go back to what we know (and kinda love...), and the next set of Areas would get a temporary/permanent "facelift." I say this because often we have to rely on the DM Team to give us this variety, but, I also think we can't put that kind of demand on the Team, either. But I do know for certain that so many Players would fully enjoy having reason to bring their high level PCs back to a low level dungeon/area, without being accused of "trolling" lowbie areas, and stealing everyone's loot with ease.
I see your wall of text and raise you by one!