On Data Sufficiency questions, you should never draw conclusions from diagrams, since the accuracy of any diagram depends on which statements you use. I've often heard and read that in Problem Solving questions, diagrams are drawn to scale unless the question states otherwise, but based on this question from GMATPrep:

www.beatthegmat.com/gmat-prep-geometry-t13546.html

I don't think that's a safe assumption. The diagram in the post above is certainly not accurate, and misleads many test takers. Perhaps diagrams were always to scale on the GMAT a few years ago, but I wouldn't assume that now.