I'd have to agree with not using it as much. I've got a lvl 10 Paladin and I've used it probably 3 times. (One of them was to put Merciful on it so the person who attacked us wouldn't die and then I hit him once to give him a cushion and tried to disarm after that)
I'm not sure going to a swift would be necessary after you change it to a move action. I guess it would be the nature progression of things but I think it's part of the balance against being able to call up some nice abilities anytime you want and not have to pay out the nose for them. I'd love to see this since Divine Bond was something that brought me to think about playing a Paladin and haven't really used it but swift would be to much I think.
Hmmm....this wouldn't help for speed of casting but what about combining this in with LOH. Casting Divine Bond takes 4 uses (you get +4 LOH at each time you'd get the ability to cast Divine Bond). This way you could get some LOH use or Channeling out of it so Divine wouldn't seem like so much of a waste. Although if you know you're going into a fight you can always call it up while everyone buffs but it's been forever since we've had that happen in a campaign.
prereq should be an odd level, as he wont be able to take it at an even level anyway.
move action and an extra use/day would be a worthwhile feat imo.
Perhaps another option would be to treat it like the Inquisitor's Bane ability. Reduce the duration to only level rounds/day, but usable in 1 round increments at will with a swift action to activate.
In a campaign I am playing, I have only used the divine bond weapon feature of a Paladin once in 9 levels (now lv 13). Usually it is more action efficient to just attack. I am suggesting a feat to allow the use of divine bond as a move or a swift action.
Improved Divine Weapon Bond
Prerequisites: Paladin level 8
Benefit: You may call the celestial spirit into your weapon as a move action. At level 11 and higher you may call the celestial spirit as a swift action, but the duration shortens to 1 round per paladin level.
Special: It is normally a standard action to activate divine weapon bond.
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Should the swift action version be another feat?
I think what you have is pretty safe, given that the paladin isn't gaining feats through class, a single feat for the reduction isn't at all out of line as it does one thing on a scaling basis of two increments. I'd even go so far as suggest dropping the requirement level to 5th and the second improvement to 10th (following when the uses of Divine bond increase) and removing the penalty of the swift action as what you are gaining isn't nearly as good as what the penalty is "worth".
Basically you're talking about "quick drawing" your divine bond.