or are some faster than others…
ex: Fletcher > Proxy > Bushwhacker ?
Engineers in general have the same plant/disarm/repair speed, but as another merc I believe you can get an augmentation that makes you slightly better than anyone else at these tasks except for an engineer.
Sawbonez, Skyhammer and Kira all have access to the Mechanic augment that allows them to repair 20% faster than the other mercs who aren’t engineers.