I do love LDoN and DoN, but that era is full of half expansions.
LDoN/LoY and PoP together works, since LDoN was very much about the augments for your PoP gear (and maybe the 1 piece you could make slightly better than one piece of time gear, maybe, if you had the stars align with the worst parts of the LDoN loot tables and needed a focus you couldnt otherwise get except from the "only on ldon raid loot hahaha" slot augments).
DoN and Omens work together too, since DoN is about a half day of raid content and best part about it (if I remember right) was Weapons that you just end up replacing most of with DoDH.
I suppose you'd do the same with DoDH and Ro, since Ro was mostly minor upgrades to visible gear the way DoDH was small upgrades to weapons and non-vis gear.
Man, I forgot why that block of expansions killed off so many end game guilds until I looked stuff up again. I remember transferring from Tribunal to Torvon because my guild imploded (and jumped to beta wow) after running into the "you dont actually get to do anything yet" Tacvi wall, doing world firsts in Omens/DoN, having THAT guild lose 20 people about 2 weeks before DoDH hit, most of them going to Luclin, joining TR and CD, and then quitting before PoR ended.
I do stand by it getting MUCH better after that, now. Group progression being a thing helped a lot.