But... I'm wondering if this would work well, somehow: our party thief, while invisible, sneaks into the enemy lair. I have Sense Link to his sight. He can bypass a lot of the ambush area and sticking points, and get near the BBEG. Now, since I can see the area, I can DD a few other party in. I could possibly DD back out and grab the rest, then bring them in.
He can cast Fog and Darkness. I wonder if there's a viable way to get some of the group into the area and get a foothold. Or maybe just find an empty room and jump into there.
Or I'm just overthinking it, maybe the fun part is battling through the baddies