At Go-ride.com we probably work on more 888s than anyone accept Marzocchi themselves. We do a lot of oil changes, low speed compression upgrades, BOS damper upgrades, spring changes, etc, but not too many seals. The seals are actually very good. I've even torn a seal in my own 888 and it still didn't leak.
If you are having leaking problems and don't have any deep scratches in the fork stanctions then your seals probably just need to be cleaned and greased.
To clean the wipers and seals:
1. Loosen the top caps and push the stanctions down until there is a couple of inches of spring showing.
2. Pour out as much oil as you can, and cycle the damper to get more out.
3. Remove the footnuts from the bottom of the lower legs and some more oil will drain.
4. Slide the damper and spring assembly out of the leg.
5. Slide the stanctions out of the lowers.
6. With a soft towel, clean both the wiper and seal. Inspect for any damage.
7. Apply a layer of waterproof grease to the inside of both the wiper and seal. I use Slick Honey, but heavier grease (Phil Wood) works too.
8. Add a little grease to the bottom egde of each stanction and carefully install. Don't just jam them in, you'll tear the wiper or seal.
9. Reassemble and fill with the right amount of oil. 210ml (same as cc) is usually right.
10. No more leaky seals.