It's a strong GOP ticket, and would put some pressure on Hillary, but the problem is that if Hillary doesn't run, or is stunned in the Democratic primaries, this ticket would actually get weaker (especially if someone like Warren, Gillibrand or Klobuchar is the nominee).
I respectfully disagree. If Hillary said tomorrow, "I am not running in 2016", I think instantly the chances of any Republican winning the White House increase even more (and as of today, I see the playing field level).
Hillary has a far softer underbelly than a Warren, Klobuchar and Gillibrand, and thus would fare worse against most Republicans, but Jeb Bush is in a similar position on the GOP side, and picking Kasich (another longtime political insider) wouldn't help one bit.