Turns out the AI only seems to read the highest Horizontal range number from the abilities that are considered Horizontal jumps. When I turned all my Jumps into +1, +2, etc., Izlude's visible range was the whole map, but he capped out at 6 or so because he ran out of Horizontal Jumps. Fixing it for him required reserving Level Jump 8 as his own custom skill and, of course, setting it to +8. Plus giving him the final vertical Jump as another +8. Didn't get too in-depth with Vertical testing, though.
Edit: Got home, did some breakpoint testing. Found where the AI runs the routine to check for the maximum Jump range. Setting it to be a flat max range of 8 seems to fix it, since the AI just ignores invalid tiles anyway.