Devil Fruits and Haki are the prominent powers in the world of One Piece, and thinking they can oppose each other in some way isn't far fetched.
As we know, the only known side effect for Devil Fruits is weakness to water, which is a low price when you consider how strong some devil fruits are e.g. Earthquake, Darkness, Ice, Magma, Light, etc... .
Shouldn't there be a major side effect ? Like minimizing how strong your haki can get to create some balance. Garp jumps in mind, how can someone with no devil fruit fight equally with Roger same as Whitebeard who ate the most destructive devil fruit ?
*Note : I'm not here to open a discussion about Garp being equal to Roger, all I'm saying is that "we almost killed each other various times" sounds like fighting equally to me.
In my opinion, this would give an answer to how characters like Garp, Rayleigh and potentially Shanks are this strong.
What are your thoughts on this?