Within the RAF, the main users of QFE are the fast jet boys, who normally take off/land from the same mil base, which uses QFE. Always landing at 0' is one less thing to think about for them after a v.v.v busy sortie with your brain melting.
When they are outside the circuit, they use QNH, so the terrain clearance argument does not wash.
RAF multi fleet generally use QNH, and we will try to fit in with local procedures, so as to avoid confusion. QNH is undoubtably the way ahead whenever terrain is a factor. For example, operating into Kabul, with high ground 13000' AAL, within 10 miles, and no approach aids/radar, knowing your ground clearance is vital.
A standard military T/O or app brief covers the use of QFE/QNH, airfield elevation and safety altitude, so this covers all bases.