Does the effect end if you stand up, or do you have to stay crouched?
Nbs will cry
Just got to test this set out on Live and it is really nice imo. I can better answer your questions now based on my direct gameplay experience.
Does it detect both sneaking and cloaked enemies?
Yes. There was a player stealthing via crouch near a siege weapon that when I popped my Sentry buff, became revealed. I have also killed multiple Nightblades trying to cloak away, as the Sentry set now provides “Truesight” and you can target invisible enemies while the set buff is active.
Does the 30 second cooldown have any visual cue so you know when it's back up?
Yup. Was able to fully answer this before and the answer is still the same.
How is the range?
My assumption was correct, the range seems to be around 20 meters which is awesome. I saw a NB fail a gank and try to flee away with cloak, I popped Sentry and they were already far away from me but I could see them clear as day spamming cloak and trying to run away. Thanks to Sentry I was able to target this player from max range with Stampede (20-22 meters), close the distance, and secure the kill. The guy probably thought I was cheating.
The range of Truesight on this set is colossal.
So yeah, what Shieldbreaker is to Sorcs, this set is to Nightblades imo.
Jorvulds does NOT increase the duration of the effect from this set because Detection is not a "major" buff. I tested this on the PTS.
You cannot test this set on the PTS without going to your alliance controlled Bruma and buying random Sentry boxes from the NPC with AP.
Yea this set is a lot of fun. It definitely has it's drawbacks though. Crouch as an activator can be a little clunky, especially with lag. Also once the effect is down the 20 second downtime gives Nightblades plenty of time to re-assess, retaliate and re-engage. Also while the Sentry buff is active, your character has very visible cues as I noted above in the images. Even though you can see and target invisible Nightblades, they can still use cloak to force miss your attacks, which you can see in my image below. So Nightblades have plenty of options against this set in my opinion.
Check out this image for an idea of the range. I had just walked through the front door of this keep with the Sentry buff active and was able to see a NB using cloak to crit with Lethal Arrows. This image DOES NOT do the range of the Truesight on this set justice. You can almost see cloaking enemies as far as players can even render, or at least it feels like it.
Go out there and grab the new Sentry set people! It's a lot of fun.
Edit: Even though my first shot / DOT missed this cloaking Nightblade, the Sentry set allowed me to continue pressuring them, hit them and ultimately kill them from a distance with another poison injection and a reflected snipe back at them. The Nightblade returned later and ganked me when the buff was down so I think all is fair.