Depending on how carefully and deliberately the streamlining is done, you probably could cut 2.1-2.55 down by half, and wouldnt necessarily require removing it out right. Some events in 2.1-2.55 are a lot less consequential to the MSQ and could be turned into side story quests that help flesh out the broader MSQ but arent totally necessary to complete. This would keep content in the game for people, still require the MSQ, and cut down time.

But it should be noted that a 25 hour reduction (from the hypothetical 100 hours) is a lot of time. Thats about 2 weeks for a player who plays a modest 2 hours a day averagely. Most MMO players easily play double that I would hazard when all is averaged out. Furthermore, ARR is an MMORPG so its going to have a large pool of playtime. If we were talking about reducing the entirety of ARR to 25 hours play time, that is a huge cut to an MMO by any standards. Even by WoW standards, someone eeked out 1-100 in about 24 hours, thats with preplanning, skipping everything, having exp gear, having equipment ready to go, having Gold, etc. For a casual player to complete all of ARR in 25 hours would be insane. Even 50 hours might be punching it to fast.

Taking a casual player 75 Hours to complete all of ARR 2.0 seems reasonable, considering the size and scope of it. Consider that it supposedly took someone about 110 hours of playtime to go from lvl 1 sprout to Ilvl 340 (with beating deltascape savage). Thats with the planning and prep. Id hazard a casual player could do all of ARR in 135 hours playing at a fairly decent pace currently and reach HW. As a point, there are 285 MSQ from ARR 2.0-2.55. Assuming each one takes an average of 20 minutes to complete, thats 95 Hours of time. Now that number obviously would fluctuate depending queue times, if a player switches jobs, cutscenes, how much they read, how smoothly dungeons go, etc, so a 135 hour completion time seems within reason.

Now I said 2.0 above for a reason when mentioning that 75 hour mark. From what Ive observed, 2.0 isnt the issue. It's 2.1-2.55 that kills people. That specific slot of MSQ is what most people have a hard time with. If pruning and streamlining was to occur, it would be in this section. Here's where most of that 'slog' sits. This is what people tned to talk about taking to long. And I would hazard that this section is shorter quest wise, but because of it's set up (with some filler and convolusion here and there), it drags on. It is not great pacing in this section and should be addressed (possibly even redone). This isnt to say we should allow it to be skipped, but that it needs a face lift.