With Shaping Focus all other levels count as levels in Druid for the purposes of Wildshaping into bigger, badder things.
Incorrect; Shaping Focus gives you a +4 to your effective druid level. With 4 Druid/4 X, you'll be at par compared to a straight druid, but any more non-druid levels and you'll start slipping behind.
OP, if you go the multi-classed druid route, consider Ranger levels and Shapeshifting Hunter, which allows druid and ranger levels to stack for purposes of both Favored Enemy bonuses and Wild Shape (uses-per-day only, not access to forms).
It's a pretty powerful feat -- 4 levels of druid, a one-level dip of Ranger, and the rest Druid gets you almost full wild shape/spellcasting, plus full favored enemy bonuses (which can be absolutely deadly if you pick enemy types that come up frequently in your campaign).