The gap is normal. It's the result of differences in how BASE shafts and other manufacturers' shafts are made. BASE blades and shafts are engineered for a tighter, stronger fit, so BASE blades don't sit the same way in other manufacturers' shafts. However, BASE blades are just as strong as other blades in non-BASE shafts. The difference is purely cosmetic. Check out this blog post for more info:
http://www.basehockey.ca/blog/the-two-piece-stick-an-underrated-solution-for-the-budget-conscious-player
Our blades are designed to fit with our shafts, so we can't guarantee a perfect look with other shafts. There should be no performance or durability problems though. Here's a comparison of a BASE blade in a BASE shaft (right), versus a BASE blade in another manufacturer's shaft (left):
I haven't had any performance issues with other manufacturers' shafts.