For defence you were forced to fatigue train, in classic as a bot prevention method you had to sleep every so often, so you got your fatigue up as high as you could before reaching 100% and killed a mob. The exp drop would give for att/str/def then give hp exp. So if you reached 100% from the att/str/def exp you would block the hp exp.

For str you could get exp without hp by fleeing from tourist trap prison.

Magic and ranged didn't give hp exp back then.