Well Haste isn't a paladin spell for starters, so you would have to dip into some other spellcaster class to get the ability to cast the spell (or use scrolls/items).
With the rule of the dice are always going to be shit at the worst opportunity, Haste is always a gamble in Honour Mode. Speed potions are safer and if you are playing paladin, everything should be smited to death within three turns.
But on tactician where you can reload, Haste doesn't come with the risk of screwing your whole run over so it's a really strong spell.
