I think it´s weird that you can raid an province without it being an act of war. And weirder still that you cant end your pacts with the raiding nation without loosing your reliability. If not to make the raiding an act of war by it self you should be available to end your pacts with the raiding nation, and maybe the nation that raid a pact faction should have it´s reliability trashed.
Also, i think that its weird and it´s very cheesy the way you can join in on wars. If you see a faction in a strong alliance it should make you think about declaring war on them- But as it is both you and the AI can just look into what factions that are already in war with said faction and ask them to join the war. And their alliance are for naught and pointless. This is a thing that should be looked at, since even though you are allies with a nation and another nation join a war against you, your ally is very unlikely to join said war if you ask even though he is pacted to aid you in just that.
BLOOD FOR THE BLOOD GOD!