I have to agree with the OP. I don't play the absolute end game content and so the new sentinel feels really good. I don't know if it will change when I'm decked out with IOs but the leveling process on the AT is very smooth and the new vulnerability feels easy and intuitive to use. I tend to shove it on a LT or boss and between movement and fighting time it feels like it has more uptime than I expected, and the snappy application feels like it doesn't mess with my attacks. With low cooldowns, moderate damage, and solid defenses, the AT solos at low levels very smoothly, and I rarely feel overwhelmed. Would a scrapper hit harder with better defenses? Sure, maybe, but I find actually hitting everything is a lot harder with scrapper, and I have to spend a lot more time chasing down runners, whereas the sentinel can blast, fight around corners, and overall just fight fairly smoothly.
I don't know if the AT is "top tier" or anything but it certainly feels better than it used to. I'm playing DP/regen right now with a character based on Alucard from Hellsing and it fits the concept perfectly. Even if a blaster is theoretically stronger my sentinel feels more stable, less bursty (so less downtime between packs), and I haven't had to actually rest even once for the first 20+ levels, let alone died, which is pretty rare for me on most ATs. I dunno if that has to do with the changes or my playstyle, but I'm certainly going to be messing around with more sentinel builds now that they aren't a chore to play!