paladin in general aims to ~900 haste only and only if he can afford the mana cost of spamming with that much haste
to be able to afford that much haste they need a decent mana pool +33k mana
then they need a bit of mp5 which helps in mana reg with +30% crit which they aim for
they would get a decent sp by then, with that level of gear and raid buffs a a paladin can reach 3k sp which makes their casts not only fast and crit a lot, but big numbers too, so their need for sp isnt that high, paladins usually aim for sp when they are in a flash light spam spec not holy light spam spec
but some get so much mana they go beond 40k and start stacking sp after that as they are already above the mana needed to keep spamming and some are above 40% crit wich means they are fine mana wise