I don’t see why it would be a problem (if anyone can inform me otherwise please do)
It would start out as a web app with the possibility of becoming an addon (however the addon part has some issues to dive into so I’m not even going to worry about that for now)
The data is completely user generated. The app only provides structure and (hopefully) some credibility to that data. There is no data being pulled from the ToS server or client, therefore there should be no violation.
I saw your post on reddit as well. To see if people are interested, you should start a Reddit Live. Maybe one for your server or one for each server. In FFXIV, there was a Reddit Live post when certain dungeons gave bonus “light” for the game’s relic weapons. That post is still being used today, although much less frequently as the relevant content is over a year old. Check it out. https://www.reddit.com/live/tlfmtjl4fteo
I honestly think this would be a positive effect as it would hurt tremendously people who have no idea about boss timers such as me. Then again i am just agreeing since it benefits me and others might not regard it the same way as i do.
Yea, I wouldn’t mind that as an Overwolf addon either if people are concerned about an overlay version.
Nope.
Not vouching for boss hunters here. but,
Being busy IRL isn’t an excuse if those people keep the timer for themselves. these are their advantages.
of course this is a good idea for the majority of the players who are busy in their life. players have their free-will to either help or not.
but personally, nope.
If ether payed any attention to anything aside his own toot the answers were already explained in detail.
What If someone got bored and messed it up though?
You know… competition.
Or what if someone decided to make the list of timers and design/program bots to auto farm them as they already do but only at specific intervals to avoid the radar…
OR what if all the bored lv 250++++ Aholes decided to 1shot all the bosses from 1-250 just to be d_ck’s as they already do but this provokes only more of them further ruining the game for others…
“Or” What if… But yet there is no good outcome of this at all.
Well you know there’s no real difference of an addon compared and to people who are in that discord server that always advertises themselves almost every few days. Claiming they keep track of the boss timers, so if you’re not going to have an addon and let a VOIP community get all the bosses before you, I’d say an addon would be helpful if you didn’t want to join in on their community or are always late on those public announcements.
To be fair though, ALL addons except though mentioned by IMC, all have risks in them, it’s just how much paranoid the person is in using them.
Only “1” addon was approved. So my hope is that this guy releases his lua script, every one of the 99% fail builds,whiners,freeloaders & s-talkers installs it. Then all hit the ban wagon the next day (including in the forums) Cheers. 
All addons were OK’d by a mod statement that as long as they are not too intrusive and greatly affect gameplay, they would allow it. Because of the vagueness of that statement, if they decide that an addon or all of them are too intrusive, they will have to make an announcement before throwing out any bans. A timer app would be the least intrusive thing you can make.
That being said, this doesn’t need to be an app. You just need a Reddit Live page with moderators. One for each server. People can post times there. Just boss and time. Players would still need to know its respawn timer, its location, will it switch floors, the spots it spawns at…
This is great so that everyone has a chance to hunt certain boss not just “Some People” who doesn’t want to share the respawn time 
I’d like to see this. This would be a great add-on for those not interesting in joining a guild.