Please reduce the RDF exp bonus and exp gain in general and allow me to explain why:
If you level a char through RDF you'll end up leveling WAY faster (there were dungeons where i leveled up 2-3 levels on a dam single run*WTF?!*) than the "gearing" process which means at higher level dungeons you will be lacking gear and if you decide to go quest it will make it worse, this happens with all my chars and if you inspect most players doing RDF it will confirm this is actually a "problem".
One way to conquer this is doing RDF queueing as specific but Satchel of Helpful Goods is something nice to have after each run making easier to gear up even though the amount EXP gained ruins process.
When you level through RDF as DPS you don't notice such impact, but when you level as Tank or Healer, specially when "75%" of the drops are cloth and you will level so damn fast which most dungeons you will end up skipping due to the fast leveling
I challenge everyone leveling a char through RDF after you reach 15 and you will see it yourself, how pathetic it can be specially if you do 2-3 dungeons(this can mean 4-6+ damn levels gained) and don't get an new item.. (dont forget you have 16 slots that require items..)
If you want to level slower, you can visit the NPC that disables experience gaining and keep doing dungeons til you get the gear you want. I don't think there are many people who try to level up just with dungeons. Since experience rates are high, most people level up with quests and mostly skip dungeons at low level.
I assume you are playing on Icecrown, so you have chosen high rate realm. If you want x1 rates you could play on Lordaeron but it has no RDF at all. Most people who play on Icecrown prefer higher rates and don't want them decreased. Most of them want to make leveling shorter to get level 80 faster. And it is faster with higher rates, even if you don't get as much gear while leveling. If you have another char already on that realm, use some gold to buy the gear you want. If not, get a profession like mining or skinning, make some gold and buy gear then.
Experience rates won't be lowered just because you want to level just by doing dungeons. Getting less gear is a well known side effect of higher rates but almost all private server realms are high rate and most players choose them instead of low rate realms even if it means getting less gear while leveling.