I only have 1 HK dedicated to buffs...the rest are cooks(great cheap food to spam in siege...yes, I am undergeared and use attack food in SW lol), crafters(all those pots come in really handy), as well as one HK that I keep at low level for essentially unlimited caviar.
also, depending on you classes, you may want different buffs depending on what you are doing or what you play. same reason to have multiple zodiacs...