Ubers is a completely different ball game. Contrary to what you say Rock and Fire moves are used quite often in Ubers but it is Shedinja's ability to stop specific threats like Kyogre and that Sandstorm is less common, allowing it to function properly.
Lugia needs Reflect or else it would be easily beaten by Garchomp. Ice Beam does not get a KO on it unless it invests an ungodly amount of SpA, in which Garchomp would hurt it majorly and if Speed is invested to outspeed Garchomp it undermines Lugia's ability to counter any Garchomp which isn't Swords Dance, or attacking on the first turn. With Reflect and Speed EVs Lugia can slam up a Reflect and basically wall Garchomp, which is important because 106/130 stats aren't enough to contend when Lugia is getting hit by a 180 BP move (Outrage, Crunch) or a 200 BP move (Stone Edge).
CM increases Lugias' durability but once again it cannot sweep due to its movepool being limited ; Two attacks and Roost, without Roost it would be fairly easy to outstall. Charge Beam is a 50 BP move, you cannot seriously use it on anything except 4x weaks because it would not do significant damage.
"Hit hard" is an overstatement. Base 90 SpA isn't enough to cause significant damage especially if said attacks are unSTABed and there is no SpA investment. Contrary to what you have said Rayquaza does min 67% to Lugia with LO DD Outrage (max Def), min 51% with +1 Outrage (no LO), and min 89% with SD Outrage, standing a chance to OHKO.
Clean Lugia Ice Beam does max 47% to Groudon, 40% to max HP Groudon. Thunder does max 40% to Kyogre. Infact, Mewtwo, Mew, Latias, Latios, Deoxys-D, Dialga, Palkia, Darkrai can all deal with Lugia. I have to remind you that Lugia can only outspeed unboosted Rayquaza, and that is with hefty Speed investment. Normal 204 Spe only outspeeds base 90, and it would have to run +Speed to outrun Rayquaza. Lugia doesn't run enough to outrun Rayquaza as it is hopeless considering Rayquaza most commonly boosts its speed.
Anyway, you are derailing this argument. Ubers is a ban tier, not a metagame, and your reasoning for not letting Lugia in OU is completely wrong, for a start just because a pokemon is "more suited" (subjective) does not mean it should be in that tier. Tentacruel is more suited for UU, must it be there? No, its OU because it is used a lot. Lugia needs 244 SpA EVs to OHKO standard Rayquaza despite the 4x weak, which is an excercise in futility.
You still have not brought up any points to not allowing it in OU other than its performance in Ubers which is in no way related to its performance in OU.