Caliborn's interlude was him as normal, before he hulked out and became LE. The current strife is long after that interlude fight, and probably on a different timeline. My current guess is John's retcon powers retcon that alternate timeline and prevent LE (or at least his current form), but I'm not sure how that would shake out with doomy dooms and all that stuff.
Or Calliope shuts off the green sun, depowering lots of people. It's been said before that the Sun powers the sessions, but we haven't really seen anything outside LE's modified sessions, so that could be a defense mechanism to keep people from tampering with LE's power supply in the important sessions he needed to exist. I also suspect LE tampered with the game itself to rig it in his favor (as his null session was designed specifically to his strengths and allowed him to win), not counting the sabotage and Doc Scratch stuff.
EDIT: There was also a few panels that explained Dave had to have Caledfwlch in its current from (made with a cueball) to even harm LE. The ghost army may just be wasting their time, or The Weapon might need to be used with Caledfwlch somehow. Getting to the fight might be a problem, though. Davepeta is really strong and even they needed a long flight to get bearings.