It would appear this thread has turned into a "hate on Rohypnol" and "Bash anyone who doesn't agree with you" Fap-Fest. To actually address what Tugboat has presented in his opinion to be a genuine problem, mayhaps arguing over how annoying or how skilled one player is against another is not the right direction we need to be headed in. What needs to be done is people need to stop arguing and submit factual information supporting where they stand, rather than the needless flow of insults and subjective, biased opinions about how they 'feel' towards one play style or another.
I play every class. I have a character supporting every 'main role' (I even have a Horse-Crossbowman) and thus I believe I can offer an objective view for everyone to consider. Horse-Crossbowman are rather annoying, yes but that does not warrant a 'nerf'. Realistically thinking however, (Although I do not know the real life specs of the crossbows in game) it would not be physically possible, for a Horse-Crossbowman to exist in real life for several reasons. One, it would not be possible for someone to pull the string into it's locked back position with one hand, unless you had a ridiculously small "Pistol-Crossbow" which would probably not even pierce armor, thus rendering it useless in my eyes. Two, even if the person is strong enough or the crossbow is weak enough for reason one to be possible, it would not be possible to ride the horse as effectively while reloading considering you would have to hold the reins with your teeth or just not at all. Three, the galloping motion of the horse would most likely throw off your loading the bolt into the crossbow, and considering the design of the crossbows in game, in a realistic setting, misfires would be common, due to the 'trigger' being a sort of lever.
I am in no way trying to say I know more than others, I am simply presenting the information that I have on how crossbows work (and don't work, for that matter) in an effort to push my standing in that reloading while on horseback should not be possible. Thank you for taking the time to not TL;DR this.
Stolz