With regard to flight sims, part of the problem is that it is tricky to program convincing rear gunner AI, and so they tend to be a bit 'Wyatt Earp' in sims. But that aside, some of the complaints from people flying WW1 sims stem from the fact that they fall into the trap of believing the often repeated tale of two-seaters being a pushover, which many were not, thus people underestimate them and don't adopt the correct tactic and a suitable level of caution. The proper technique involves a lot more than most people think...
It is true that a two seater could be defeated, but you have to use the fighter's superior maneuverability to do it. Even so, things were not as simple as many accounts would have you believe, and a determined two seater crew with good teamwork could cause real problems for a single seat fighter going it alone, this is in fact why the DH4 was not as good as it could have been and was redesigned, since the widely separated pilot and co-pilot marred cooperative crew communication and forced it to rely on crossfire from formations, though that too was effective. Nevertheless, it is worth noting that when WE Johns' rear gunner on the DH4 he was flying was killed, he was able to hold off numerous Fokker DVII fighters for some time by throwing his DH4 about in quite a display of aerobatics. Morevover, if there are a pair of two seaters with good combat spread separation at slightly different heights, it is difficult to get in a firing position without being exposed to fire from at least one of them. Check out some of the kills achieved by
Independent Force DH4s against fighters, and you can see that it was not quite the turkey shoot for the Germans it is often portrayed to be.
Of course everyone knows the bit about firing at two seaters from underneath, so that the gunner cannot return fire because the attacking fighter is shielded by the horizontal stabiliser of the two seater, but the bit people forget is that you should use a different technique on the approach and especially if the target turns. The moment a two seater turns, the instinctive thing many fighter pilots did (and still do in flight sims) is to turn with it on the inside, as you would against a single seater trying for a tracking deflection shot. This is not the correct thing to do, as it allows the rear gunner a clear shot on an effectively stationary target, and with your engine and prop being what he will hit. The correct technique is to dive and turn in the
opposite direction, and then turn back toward it coming in under the thing on a wider radius. What that does, is uses the two seater's fuselage to block the gunner laterally when the two seater is banked in a turn, effectively keeping you 'underneath' it when you are in fact off to one side. Here's a diagram of the correct flight path to do that:
Al