I have seen at least one other post asking about it. The answer was one that I concluded via my own testing as well.
(
https://www.ddo.com/forums/showthrea...he-Patron-Pact)
In short...
Question: How do I change my pact?
Answer: You can't.
Response: That's dumb.
Allow me to elaborate.
I have been running the Warlock since it was released on Thursday, June 18th, and I must say, I really do love it. I think it is a fairly fun class. Not a do-all, end-all. Decent balancing; garbage saves. Anyhow, that's not what I'm here to speak about.
I have been running in the Great Old One Pact since my first Warlock life, mainly because I liked the idea of the saving throw being a Will save: something that hopefully not many end-game monster would be able to make. Well, I think I was wrong. Unless you are specifically shooting for maximum Charisma and Difficulty Checks, Warlocks simply don't allow you to overcome end-game Epic Elite monster's saves. This was no surprise. That's how it should be.
So I figured, "what the heck, why not try Fey Pact and the various spells and abilities it's packaged with."
So I make my trip over to Fred, thinking, "oh this should do the trick!" Needless to say, I was sorely disappointed when I realized that I couldn't switch my Pact! I searched the forums, and the conclusion was one that I feared:
you can't change; how dumb is that!
The only way to change your Pact is to (1) use a Lesser Heart of Wood, or (2) True Reincarnate (or Epic Reincarnate).
The answer on the thread I previously referred to asserts that having to use a Heart of Wood isn't "an unfair requirement," providing that "Lesser hearts drop randomly and can be traded and bought."
I simply cannot agree with this. Lesser Hearts are not a common item. They don't drop like Blood of Dragons; they are very rare and therefore very expensive.
So while other classes can change the damage type they focus on (melees can simply equip a new sword, rangers can equip a new bow, and spell casters can quickly reset their Enhancements or use a Blood of Dragons), Warlocks are stuck with one Pact. Permanently. (Save for the highly costly options I listed above)
I'm not saying that changing your Pact should be as easy as swapping your equipped weapon, nor as easy as swapping a spell. Your Pact is intimately bound to your character and shouldn't be something you change daily.
I do however think that it should be an option for those wishing to try something new. I believe it should be as easy as swapping a single Feat, or perhaps implementing a new drop, similar to Blood of Dragons, that allows Warlocks to switch their Pact.