Personally, I wouldn't play with the off-set on the '04 KX250. It is literally one of the best combination of handling characteristics on an MX bike/off-road bike I've ever ridden and I used to sell them (and have ridden a bunch on top of that). I wouldn't mess with it just to get a DLC fork coating, even as cool as it looks (I doubt there would be a major improvement in fork feel, not enough to off-set the off-set). I'd say if you're not a 100% happy with your suspension action, even giving the concession for varied conditions in the same race/day and the compromise off-road we have to balance (like riding South Jersey sand & hardpack, or New England rocks & sand, etc), I'd possibly look into a different suspension guy, preferably one closer to you with a lot of experience in the regional terrain you generally ride or race if your not 100% happy with the valving.
On my own '04, I have tried a mired of suspension combos over the years, my current favorite for my application on my '04 KX300bb I race/ride east coast off-road with in the A class is a WER revalved '03 KX250 forks & a WER revalved '07 KX250 shock. The forks have SKF seals, are serviced (along with the shock) at least once a year or more. This combo has been a phenomenal set-up for me off-road, plush enough to eat trail junk & still go straight through the whoops and enough adjustment to be super compliant in the rocks to boot. I also use Flexx bars & a WER dampner which are the icing on the cake.