You know when you don't deal enought damage to the boss and you get slayed for it? Well, it can be a big problem for engineers that camp in one spot and it's also useless becuase you just need to make 3 dmg (after the message has appeared) for survive, thing that is not easy for an engie that uses rescue ranger + wrangler. So i'm asking to remove the slay (for the damage) for everyone, or only for engies.

I am certain the mechanic was introduced exactly for the purpose of preventing turtling engineers hiding in obscure spots and not helping the team fight the hale in question (as well as timewasting scouts of course).

I very much doubt Frog will remove this feature, as it is quite effective in dealing with this exact problem.
If anything, a slightly more visible message other than a one-line chat message, easily missed if focusing on the boss, might be helpful. I have died a few times to the autoslay when I'm running around as spy shooting from afar, if the boss is running in an inside area.

Other than general unawareness of the time left to get slain though, I believe it to be one of the better devices present in the server.

The problem is that engineers haves this type of gameplay, staying in a spot with their level 3 sentry ready to fight hale but this slain often kill em, today i made 13000 damage as campineer becuase i made a sentry IN THE MIDDLE of the battlefield and the boss didn't saw me so the sentry made 600 damage and i didn't got slayed. The slain for no damage is an huge pain in the neck for campineers and it should be removed. At least for engineers. You don't know how many times i could win but i got slayed for no damage

Flood...

It sure is pain to die when you got a full nest but, well, that is your own fault.

We need that. Not just for the useless players, also for the AFKs and timewasters.

They're not a problem, timewasters just need to do 3 dmg for survive so it becomes useless, there are also regs that can voteslay em and, in most maps there is the 2 minutes limit and the anti timewasting people capture point and afk are moved to spectator team after some time. The slay for no damage is just useless and painful for engies.
(Edit)
And tell me, why an engineer should risk his life for deploying a sentry in the battlefield or for trying to shoot to the boss ?because there is that rule. I cannot count how many times i died in that way

Or move your sentry?
Or don't play engi?

Moving the sentry is even more dangerous! You're slower and the boss can destroy it easily if he sees you when you're building it! And please i want play as engie and there is no reason for not playing him, unless there are low players or there are bosses like seeman or it's a bad map for engies of course but, if used well he can be the hale's nightmare OR che can help other teammates with the dispenser and his sentry. Ask to verus-wiseman or kavey if this is true, they know it.