If a player gets disconnected at some of the last rounds of a match and the match gets over before their 3 minutes of rejoining time, they should not be issued a cool-down and should be allowed to join the next map or any other servers(if they intend to do so).
This is fair in my opinion and is followed everywhere else too. Please implement this disconnection exception scenario. Thanks in anticipation!
While implementing cooldown the place where I couldn’t decide was a possible abuse for this. If I am in a team losing 1-14, and 3 people rage quit (because they know they won’t get a cooldown) all my chances of attempting a comeback are gone. So what to do?
I might suggest a solution for this but it would cost you some money 
Jokes apart, I understand that there could be too many deadlocks which we might face while resolving any issue but we should be on a point where the new issue is so small that it can be neglected or has a work-around.
In this case we can easily find out if the player disconnected and was not timed out due to any other issue and hence should be punished with a cool-down but a smaller one (not 30 minutes)
Anyways, I am going create 2 more threads which might address the solution to your question. Thanks!
Well the problem is that leavers are known to very well just pull out their network cable or turn off WiFi to simulate a time out 
haha, that’s true, but in the current scenario, the player will get a cool down even if he disconnects at the last round when its so evident that the match is going to be over and what is more horrifying is that it applies to the players on both the teams - Winning and Loosing.
Anyways, as stated above I have created 2 more threads which might address the question you have.
To Conclude: This is just a PUG, so its not that serious for many players and they are ready to take a cool-down anytime, intentionally. Implementing the suggestions provided by me might just help the players be a bit happier and play in a even better environment (i used even there as you are already doing a great job 
).
I better be back to work now else my manager will kill me . Thank you!