CCP implemented a five-second delay because players have previously abused the REs during the precursor build. Take that into account the next time you plant explosives. On the brighter side, they are still rather effective towards preventing hackers from getting your objectives.

Sensei was taken.

I am talking about prox mines not remote. Remote are still as good as ever. I have had a lot of trouble with prox mines though. I watched a LAV run over the section of road where I had placed 3 prox mines and it did nothing, but bump it like a speed bump (on multiple occasions).

If an LAV rolls over a mine at full speed, it will generally only receive splash damage as it's usually left the primary explosive area before it detonates.

So a tactic I like to use is to place all 3 mines in a triangular formation with a couple of metres distance between them.
When a vehicle hits one of the mines the resulting explosion sets off the other two, and then well the LAV gets vaporised, and maybe even an unprepared HAV.

Also, if I'm running with my special logi rig setup, I do like to chuck a nanohive on top of the proxy mine as well, not only does this disguise the mine, but also it sets a little booby trap for any of those little red dots that are playing the team game properly.
When they shoot the nanohive, it sets off the fireworks.
But that's a secret, so ssh don't tell anyone.