[Imp]

Pat terrain will make a big difference as mentioned if Oplot is hull down for instance. Also Oplot has a pretty good ammo loadout and accuracy so if it gets a chance it could fire at range. No chance of destroying but will hopefully trigger ERA.
If terrain allows one group can strip ERA safely at ranges over 2500m and possibly draw fire then other group pops out at closer range to kill.
AP Artillery is also effective at striping ERA although its pot luck what facing it hits.

You need to be warry of getting into a tank duel with any vehicle with ERA 7+ as it will probably survive the first shot. Its a bit like playing WWII where they quite often survive the first hit except the return fire is a lot more accurate.