[Dendory]

The problem isn't adding levels. You can do proper raid itemization regardless if you have levels or not. Take a random EQ expansion, say Omens, which did add 5 levels. People in crap gear could exp in 80% of the exp zones, but they had a hard time still in the highest level exp zones. And there's just no way they could walk into the trial zones, much less Anguish, without getting their ass handed to them. The vast majority of guilds at that point still worked on Time, on most GoD content (which says something, since most people seemed to hate GoD) and then worked on Anguish keying.

Noah said it best, when a new expansion gets released, you should expect group players to upgrade their gear with new group content, and raid players who raided the previous raid zones to upgrade their gear in new raid content. You should NOT be able to upgrade your raid gear you just got in new group content, same as you should not be able to go straight from group content to high end raiding skipping all previous raiding zones. A typical PoTime item would not be upgraded by group content in LDoN, GoD or OoW. It could be upgraded by DoD group content. That's 4 expansions, the way it should be.

It's not rocket science. Let's say your PoTime BP has +250 hp, while your typical group player playing in PoValor has +150 hp BPs. Well your next expansion should provide +190 hp group content, and +290 hp raid content. The one after that +230 hp group content, +330 hp raid content, and the next one +260 hp group and +375 hp raiding. That's how you do it and keep both casuals and raiders happy, yet don't make raiding previous tiers meaningless for 3-4 expansions at least.