Yeah. In other words: it was realistic.
I think some people are used to FPS aiming where high energy particle scientists can pick up rocket launchers gauss guns and immediately know how to fire them 100% accuracy at small, fast moving headcrabs.
The Deus Ex system is the best thing available when you want to introduce RPG stat elements into the game because it's still based on your skill. Bloodlines's system was atrocious (auto-aim, and your chance to hit randomly decided) - you could shoot point blank and still miss.
ERrr, what Bloodlines game did you play? I had neither autoaim, nor was my chance to hit randomly decided as the crosshairs proved to work identically to Deus Ex's. Heck, the Colt Anaconda even reflected this and the crosshairs would get so tight the gun was precisely accurate.
And yes, Deus Ex's weapon skills (and Bloodlines), reduced the maximum size of the crosshairs as you improved your skill, in addition to making them shrink at a faster rate, to a tighter minimum. It made perfect sense in both games IMO.