Not too much harder. We're already used to having to rejoin after dying, and having our mons 1 hit by undodgable Charged Moves.
Even though Groudon is easy to beat, my team (as well as everyone elses since I'm a pretty high level) usually gets wiped once. The timer is pretty fair since Exeggcutors and Gyarados have pretty high attack, and Clear weather makes the fight more interesting always.
Best part is everyone has high level Exeggcutors following the Weather Update.
Most players don't care, they just want legendaries given to them, then they can show them off on social media!!! Which is exactly what Niantic have done.
How can a legendary be taken down with three people? Ridiculous, but not if you're a noob who wants everything easy.
If you want a challenge GO is not the game for you, it's no challenge.
Sadly, that's not part of the current game. It's about numbers. Get this many decent trainers, you barely win. Get a few more, it's not so hard. Add a few more, and it's easy. The game seems to be about how many people are or can be at a raid, not whether they are good or not.
Personally, I work to carry my weight. Powered up another Gyarados to deal with Groudon. I could have just gone in with 6 Vaporeon or 6 Exeggutors, and let the numbers carry me through the raid, but I want to contribute.
Lugia doesn't need a nerf. Ho-Oh has a high BST and good spread of stats, with a high attack stat. Ho-Oh got screwed out of STAB, but at least it carries some type-relevant moves. Lugia didn't get a Flying-quick move, and Psychic DPS remains with other Pokemon.
Lugia doesn't have the best Attack already in a game where Attack is king. It's my favorite Pokemon, though, and I love a defensive approach to things. I don't think Ho-Oh fulfills the same role, for it can put out a lot more damage and cover a few more types, albeit without STAB.