Generally, that is correct, one should not fight on the road.

However there is something to be said for goading 2 or 3 or more of
your enemies to chase you down and try to kill you. Those are
enemies that are going to waste time on you, than are going to be
trying to cap flags.

I often "taunt" the Horde, and get some of them to come out of their
group to chase me. It's quite fun but I expect only noobies fall for
it anymore.

"Fight on the flag" is not universally good advice for Tol Barad. Because of the way flag-flipping works, once the attacking team controls two towers, each attacker is worth more than one defender. If the defenders can stall the attackers away from the flags, this will decrease to chances of the third tower being taken while increasing the chances of taking back one of the first two.

If you're trying to defend that last tower, fighting on the flag is the worst possible strategy. The attackers don't need to win; even with a smaller attacking team, they just need to stay alive long enough to push the marker. Each attacker you keep away from the flag by fighting on the road is a proportionally greater loss to their side and decreases the chance of your side losing the flag.

The inverse situation is true for attackers at the start of the match: if you can lure defenders away from their flags to fight on the roads, you can take that flag with a proportionally smaller team.

@Scott Clark: I think you've hit the nail on the head: "Fight on the flag" is the advice to whoever is trying to cap the flag. "Distract them off the flag" is the tactic for whoever is trying to retain the flag.

If the flag's defenders can lure the attackers off the flag, then it doesn't matter whether any defenders stay to "defend" the flag, only the attackers can affect it. As good, if the scrum is "placed" well, the healers for the defending force can stay in back "on the flag" while the rest of the flag defense keeps the attackers busy.

I have to agree with that. I think it's still overall more beneficial for defenders to fight inside the keep than on the road, in most cases. You don't want to get too far from your team mates and find yourself isolated too far from where you could actually make a difference. So, as a general rule, with a few exceptions, fighting on the road is less than optimal.

If you can coordinate your actions well enough, then fighting away from the keep isn't a problem, but this isn't usually the case.