I'd love to say I've had diplomatic crises in EB/RTW but I haven't. Any nation I border attacks me at some point and I know the AI is as dumb as a sack of spuds and incapable of using diplomacy. This remained constant until Shogun 2, where I actually have lots of them in every single campaign, which is how a TW game should be in my opinion. As the Uesugi, the clan just below you that is a protectorate (that I'm convinced exists only to draw you in to as many wars as possible) is constantly attacked by your neighbours. Do you:

A. Refuse to help your allies who you previously promised to help (thus the protectorate) and take a huge blow to your Daimyo's honour or
B. Join in yet another war when you can't even handle the 4 you're already embroiled in?

Always a fairly impossible choice that will most likely end up with you being wiped out, no matter the campaign difficulty you're playing on. Unfortunately EB/RTW just isn't able to offer any kind of diplomatic cleverness even close to this.

I guess what I'm saying really is... I've never had any.