The bidding was reasonable until West's 5C bid (I might have bid 4C instead of only 3) but when East can compete to the 4 level over the forced 3C bid, West's hand is obviously worth bidding 6C. West 100% of the blame. I wish I could give him more.
What's the 3D bid all about? That should show about 6-8 and a good 6 bagger in diamonds. Isn't 2NT forcing? I certainly wouldn't want to play a system where it could be passed. Now you would get to 4H on the 1st hand and 3NT on the 2nd.
I also agree with Cherdano, especially his point that you have to have a way to differentiate between 'gambling, preemptive' splinters and real ones. With the given hand repeated club leads would make it depend on a trump split and a diamond split.