It really depends on your shard. When people say 300+, they usually mean displayed speed, not counting his leadership (I think - this may vary from person to person). 280+ would be fast enough to get into the top twenty on my shard, but probably fall to the 40s on defense. The fastest Revans I've seen have been in the mid 320s, tend to stay in the top 20-30 on D, and I assume are taking top 5 (if not first) at payout. Check the top Revans in your shard - that should be your short-term goal.