Well, let's see. They stated their intent with DLC for Skyrim (moving forward from Oblivion and particularly Fallout 3) was to have fewer DLCs that had more content within them. In the same interview it was stated that despite the positive reception, the resources they put into Shivering Isles didn't really pay off, so I'm afraid we won't see another expansion the size of Shivering Isles again.
They do seem to have a trend of going for one small to medium sized expansion, and then finishing it off with a large expansion, with little stuff in between.
Tribunal wasn't a faction-driven expansion - it was an expansion in the same vein as Bloodmoon, Dragonborn, or Shivering Isles, simply on a much smaller scale. It gives you a huge city to wander, a story-driven main quest (that isn't centered on a new faction like KotN or Dawnguard), and tons of side-quests and new toys. Knights of the Nine is probably the smallest "expansion" in the series that isn't a "minor" DLC - all it had was the one faction questline and set of armor, although that's not to say it wasn't an excellent expansion. Dawnguard might be on par with Tribunal in sheer content; aside from a great main quest, it had tons of faction-specific radiant quests, two worldspaces on par with Blackreach in size and detail, and tons of great items. Not to mention the unrelated stuff that's just thrown in for free, like the werewolf perk tree or the quest for the Aetherium Forge.
Then there's always a DLC that adds a new landmass to explore, and puts the bulk of the content on that landmass. Bloodmoon didn't have as many great new items compared to the others, but the East Empire Company questline was fantastic, and the main quest was really well-done. Shivering Isles is probably the biggest and best of these kinds of expansions we'll get, though I'd be pleasantly surprised if I'm proven wrong on this one. Dragonborn has the shortest main quest, but it also has a ton of awesome side-quests, and some of the best gear and bonuses I've seen so far: I think it's a really great indication of where Bethesda's going as game designers.
Then we've got the little things. Bethesda has a few random mods for Morrowind that are free for PC users to do whatever they want with, but the general consensus is that these mods range from okay to kind of awful. Oblivion's little content packs are all over the place; they're all fantastic except for the infamous Horse Armor, though. Hearthfire is great if not painfully buggy (they need to figure out a system where they can actually patch their DLCs), and they also added some free content like ranged kill-cams, mounted combat, and Legendary Skills (!). Did any of the patches for Morrowind or Oblivion add free stuff like that?
It should be noted that DLC as we know it didn't exist when Bethesda released the expansions for Morrowind - digital distribution wasn't widespread enough, so they had to really focus on making a couple of expansions that were worth it. Overall, I'd say Skyrim has the most cohesive batch of DLC, and I like the path they're taking. Not sure I like the implications of them giving Xbox owners first dibs, though, although I'm confident Bethesda won't screw us over with overtly harmful business practices like some other devs have.