Poyudi Hytori
CL does not effect luck. But if your level is too low or too high it nerfs drops. (Say you have a 60% chance at CL 11.4, you'd have a 15% chance at CL 12, or a 30% at cl 10.) 11.4 in yellow maze is the "sweet spot" for drops. Meaning you have the highest chance around there. I would guess about 65% - 70% of the time you get a orb dropped without any luck bonuses. With those two rings, Major luck, and R4 buffs it's about 90% or 95%. Add in Fitness as well and it's definitely 100%. honestly, with the two passives there might one enemy every 4 to 5 rooms that doesn't drop an orb. I haven't actually tested it. (And I might test it to be honest.) But this is my best guess.
That's what I was referring to as "conning issues," yes - 'conning' is the process by which one determines their drop rate from a given enemy, based on relative levels; you can tell by the colour of those enemies' names while targeting them. However, as far as I'm aware, there is no level where drops are quartered (your 15%); enemies conning Green and Yellow drop normally, enemies conning Blue drop half as well, and enemies conning Red and Purple drop nothing at all. Furthermore, the reason that 11.4 is used for Yellow Maze farming is not that it's actually the "sweet spot" on its own (CL 11.5 would be the highest one can be while conning Green to CL 11.0 enemies), but because it's as close to the "sweet spot" as possible without conning Red to CL 10.0 players (which would completely eliminate their drops). So long as your no-one in your Crew is CL 10.0, CL 11.5 should work just as well.
As for drop rates, I'm mostly convinced that the base drop rate for Shadow Orbs is 66-67 (I'm not sure whether the game handles decimals, but it'd be around two-thirds of the time), which roughly accounts for the 90-95% approximation (91-93%). However, any testing you could do to make that estimation more accurate would certainly be welcomed... 3nodding