Soon, Lugia will get its signature move Aeroblast, which boasts an eye-popping 180 base power, and a similarly massive 75 energy cost. To keep this analysis simple, I ignored the 12.5% chance of raising Lugia’s attack by 2 stages.
In summary, Aeroblast is basically a strict improvement as a secondary move over Hydro Pump (with the other 2 moves being Dragon Tail and Sky Attack). Aeroblast adds wins against Togekiss (1 shield), Kyogre (0 and 1 shield, bait-dependent), and even Shadow Ball Mewtwo (0 shield). The only losses it adds are against Rhyperior and Heatran, both of which are much rarer than the Pokemon Lugia adds wins against.
Lugia with Hydro Pump ranked 16th of 33 in PVP IV’s rankings. Even without Aeroblast, Lugia was borderline usable in Master League thanks to its excellent bulk. It’s arguably the best Mewtwo counter (so long as Mewtwo doesn’t have Shadow Ball) and can reliably beat some other popular picks including Groudon, Dragonite, and Giratina Altered (Dragon Breath variant). However, losses to Dialga, Melmetal, and most Giratina variants hold it back from being a staple of competitive play.
With Aeroblast, Lugia will rank 5th in PVP IV’s rankings, but it doesn’t offset any of its major losses mentioned above. 5th then seems very high, but keep in mind that PVP IV’s default rankings are not weighted, which means that losses against Dialga, Melmetal, and Giratina don’t factor into this ranking as much as they probably should; that particular team of 3 is very common and Lugia is basically useless against it.
Additionally, simulations tend not to be very realistic when it comes to baits. Even though Lugia can beat Togekiss in the 0 shield, players will often bring Togekiss in with shields remaining, and it will be unclear whether or not the player will shield, which means Lugia will not know which move is optimal to use. In general, simulations are overly optimistic about very expensive moves, and this is no exception.
Anecdotally, I predict that Lugia will fill a role similar to Dragonite, with the main difference being a loss to Giratina instead of a loss to Togekiss. It will appear occasionally and have a well-defined role, but don’t expect it to compete with mainstays like Dialga in the top tier of Master League.