You can't be serious. Lugia is base 110 speed, 106 HP, 130 Defense, 154 SpD and has access to Roost. It can wall most of the OU tier especially seeing it has pressure which would make it weak to only Dark and Ghost attacks. It would be extremely difficult to play around Lugia especially seeing Lugia has a respectable base Attack/SpA of 90. Lugia also learns Whirlwind letting it be what would be the greatest phazer in the OU meta game.Those pointed stones sure taste lovely, lol. The bane of Bug/Flying, my favourite typing.
By the way, I think that the Defensive Characteristic of an Uber sucks and is really flawed. EVERY defensive pokemon can be set up on in some way, and therefore, people use the argument "play around it it". You can play around Blissey, sure. Play around Lugia? Yep, you can still do it. In fact, if Lugia was an OU (I'm not advocating this), people will simply play around it the same way Blissey is played around. Lugia walls no more physical walls than Blissey does special walls. Blissey stops NPlot Azelf, non Choice Starmie, Empoleon, Jolteon. Offensive cune. People have been playing around Blissey for so long, they forget just how many Special Sweeping sets are completely unviable due to it. Lugia would stop all +Speed Sweepers and pretty much all slow set up sweepers. It would overcentralise the metagame, just like Blissey has, and make people play around it the same way you play around it in Ubers.
In short, I find that the Defensive Characteristic is very pointless as any potential suspects are not given the treatment from this clause simply because playing around it is too easy. Apart from the so called "obvious Ubers' like Giratina and Lugia, no Pokemon has ever come close to being banned for the Defensive Characteristic. And I would imagine that if those 2 Ubers were in OU, they would more likely be banned for Offensive and Support Characteristic simply because it is harder to play around Draco Meteors and Calm Minds.
Giratina has base 120 defenses and 150 base HP. With a great tying of Ghost Dragon it is a great threat. It even has base 100 attack stats and can phaze. It may be lacking an immediate recovery move excluding RestTalk. Even then though Giratina can be a huge threat with its bulk, it can wall the majority of the metagame that does not set up and even those it can Roar away making it very, very bulky with Rest Talk. It can easily either wall as a RestTalker or phaze, but in the OU metagame it will probably be a mixed attacker and become Ubers for the Support Characteristic. Lugia will probably become uber for the defense characteristic if it were in OU.
Both are defensively focused due to how they would be outclassed by other pokemon offensively which forces them to be more defensive.