Paladin and INT Q.
 

I know INT can increase the amount of damage done to a spell. Does INT also increase the amount of healing done as well?

Yes, it increases healing done with the healing spell as well as the resurrection spell.

It also increase % of units phantom gives, how many demons demon gate summons, how much leadership hypnotism can charm. Unit bufs or debufs only get one more duration for each 15 int. Most other spells get more effective with more int. Of course there are exceptions like Phoenix that as far as I know doesn't gain anything from int.

Actually int doesn't increase the % of phantoms... its always capped at 23/33/43% of the units. However, int still helps phantoms as every 15 points lets them last 1 extra turn.

Overall int is still pretty important for paladins, but you shouldn't overly invest in it, as you rely much more on units/rage spirits to kill units. Generally I've been using phantoms, resurrect, mana spring, and geyser more than anything. I still use other spells if the situation calls for it, but those are the best ones to me.