Here's the problem though, ok we make all meltabombs have a setup timer, lets say with this nerf we make eldar meltabombs capable of almost a 1 shot on rhinos (so it's only a quarter burst of fusion to finish it off to be on par with how fast wave serpents die)

The problem comes from if they become to damn hard to place meltabombs than Eldar are in a GG to bad tuff scenario as rhinos still have 40% more HP so WHEN the meltas fall out of favor Eldar are relying on the Reaper Launcher which isn't a 3 shot on Rhinos like the Lascannon is on WS.

Basically we don't have a super strong ranged AV option for when we can't place a meltabomb due to setup times. and that will shift the AV advantage massively in the other factions favor

I agree, it feels better to use just for actual AV giving up TTK for losing a target lock for a chunky target while having flight time makes it worse for that role, and it's because of that it will never be used for AV, It hardly did a good job without a cooldown after all, pretty sure a meltagun has a faster TTK on tanks in comparison.

It is nice for quad guns and that's all the AV it will be good for and that's just because they can't drive off in the 6 seconds it takes for the next shot you have to angle and curve.

Also if there is an option to disarm the meltabomb, it should require pressing e (standing next to it) rather than shooting it. Shooting it doesn't make any sense, and it'd be easier to disarm than set.

Another thing to consider is that meltabombs do not prevent the vehicle from moving like powerfist smack does. I don't know how it compares to gravgun as far as utility goes, but it is more than meltabomb has. (I have never had a gravweapon unlocked to try)

When fighting Vehicles in an Eldar vs Other match, vehicles are dead soon.

1) They kill your vehicles fast
2) Their vehicles get killed fast.

That's what i somewhat dislike when playing/fighting Eldar. A lot of running

I would suggest 2 things:

1. Melta Bombs for Sergeants only with a special loadout selection similar to the Elite (Veteran). So it is limited on the battlefield, but can still be powerfull
2. Make it with an internal timer (30 secs?) and, like @Sumshine said, press (E) to disarm. Maybe alternatively press (G) once to place it and press (G) again to detonate it.

So make the squad leader the only one capable of full AV, and make melta bombs take half a minute to detonate. Do you know how much time is lost in half a minute in this game?

Edit: I should clarify. I think your suggestion needs tweaking.

other than eldar being able to carry 2 and instantly kill vehicles with one person, melta bombs arent too bad imo, maybe a slight nerf so you need 3 to kill a vehicle and not 2?

Yes, similar to Tabletop. High power weapons or equipment should be limited. About the timer, let's make (n) secs and is up for discussion after testing (is was a number with an "?" so no need to take it full) And again if it doesn't work, let's make a manual trigger, so you decide when it goes boom.

That would still make the squad leader force themselves into the role of an AV tactical. One melta bomb is equal to two meltaguns firing in unison and when a tank is in combat or orks are pouring out of a trukk the last thing you're going to have time for is to stand around firing melta beams. This goes double for quadguns.

Also, I realised I came off as a bit of an ass in my last response. I edited in a section trying to explain myself better. I won't renege on my statement that 30 seconds is a long time though. Sorry about that.

In tabletop, Meltabombs are a squad-wide upgrade, anyone can carry them.