The cascading alliance/guarantee war issue is indeed a bit annoying sometimes. I usually play with AI agressivity at less than normal, which solves it to a certain point.
In general, EU3 offers a lot of fun and many addicting gaming hours for its money. You can even learn something about history. Definitely go for the chronicles version that includes Divine Wind! Compared to Victoria, EU3 is more focussed on diplomacy, macro economics and grand policy, while Vicky concentrates more on micro economics and social issues of the time period. Both are empire building grand stretegy games and worth to be played.