You're not going to know until you get it blasted, but my gut feeling is that it will be OK.
Both my DT125A and YZ125X had areas that were this ugly, and (after repairs) they've both been fine despite some fairly hard use. The little DT, in particular, lands from jumps like a bag of cement and has a pretty crappy looking construction under the engine. I was a bit paranoid about it through the first few meetings, but there's been no signs of drama.
Like Vandy said, they're made from very thick walled tubing, so some pitting isn't automatically enough to render it useless.
And because they seem to be fairly low grade tube, welding up holes/pits doesn't wreck the grain structure of the steel.
