The game has replayability in terms of its branching storylines and alliances, but I'm not 100% sure I would replay it, just for myself. I am curious about those stories I didn't get to try, but not sure I'm inclined to deal with the aspects of the game that were frustrating or underwhelming just to see them.
That's my concern with all RPGs and almost always leads me to dismiss any thought of replaying them. Seeing as you've only played this once, you probably won't be able to answer this question, but I wonder, does Tyranny have actual replayability in the sense that a new playthrough doesn't just mean a different character class and a few different dialogue option, but a completely different turn of events, new areas/missons/quests and not a huge amount of repetition in narrative and objectives, mostly?
To some extent, yes, though it's not really open world either. The game is in 3 acts (and there's a "Conquest" section before the actual game that's a short selection of binary choices, but that will impact the game world and the resolution). In the pre-campaign, there are choices you can make that will make areas within certain zones accessible or not. So to a point, yes, parts of the game world will be different based on your choices.
The main quest of Act 1 appears to be more or less on rails, though there are zones for side quests you can visit/skip. But you can handle it very very differently. For example, you're part of the Empire, essentially, which has two dominant factions that are feuding with each other while in theory trying to conquer neutral territory.
So you can ally with one or the other, or try to ally with the neutrals, or go nuts and just kill everything. But it does not appear that the quest line changes. Still, I thought I was playing it in such a way as to straddle both factions, and then ____ happened and I had to choose. But all that work wasn't entirely wasted based on how it impacted my relationship to my companions.
Act 2 has 4 main quest lines (multi zones in each), and if you ally with either faction you do 3 of the 4, so there's a line I didn't even do, though I did pop into two of the zones just to capture the tower. Apparently if you go full chaos mode you do all 4 quest lines. There are a total of 10 or so factions, and depending on who you aligned with or didn't of the 2 Empire factions, other factions will respond to you very differently. For example, one faction who should have been sympathetic to my character and playstyle, made me slaughter them only because of who I was allied with, versus being able to negotiate a truce and safe passage.
Still, you have a core objective for each mission, but there are a number of ways to resolve it. In one case I could have resolved a key main quest by murdering a baby (hooray?), but there was another path to resolve it because of my lore skill (or alternately if you play the library quest line and find a scroll first, that can also save you from baby murdering while still achieving the objective). I did not test what happens if you don't have that alternative and don't wish to murder the baby.
So yes, it's dystopian, and you have to make some really awful decisions at times.
Act 3 is the reckoning of everything you've done to that point, so you could play it very differently - again, only to a point. If you handle the assassin one way, you'll fight him in one zone; handle him any other way and you'll fight him in the citadel, but it seems as if you can't get around fighting him somewhere. But of the three other primary archon opponents I killed one and subjugated the other two, and there are a number of permutations available to you there.
Beyond that, I'd probably have to refer to someone who has replayed it to tell you how different it actually is, but I'd say it appears to be at least moderately robust in that regard...maybe.