Something to consider is the Daggonoths in the tower from where you do the quest "Horror from the deep". I trained there forever, but from 110-123 f2p combat (in 2005) I did slayer
Quite frankly, the only use I see for slayer is for those player who like a variety in what they are training on. Indeed, it may not be for everyone but it makes the game more interesting instead of having everyone AFK all the time.