For what it's worth, you don't have to make the same level of investment that I do to get a workable DC. You could easily drop 10 points and still be able to reliably assassinate casters at endgame. When I invest in a DC ability, I want it to be near no-fail or I won't bother. That's just my own personal preference. So you've got plenty of options to get an effective assassinate. It's entirely up to you if you want to use them or not, but they're there nonetheless.