Agreed on multiple points.
Harclave (done right) is by far the best time/exp value of any quest in the game.
The arena is still a somewhat fun trial of your solo skills. (although with AA points it's a lot easier than it used to be)
The teleport stone makes this a free trip to the TS docks if you can evac...and if you can't, it's only a griffin ride away.
You'll get a free lvl 20 spell that will probably replace 1 of your other normal spells. You will not have to upgrade this as it scales with your level. (e.g. If you're a fighter, you'll get a new single-target taunt that you'll never have to buy upgrades for)
If you're having trouble doing Harclave in less than 9 minutes, do a search for Harclave in this forum and there's multiple guides. Basically, you want to invis to the arc, then head to shroom king, pull and kill in a distant corner, reinvis and then go reclaim the throne...so only about 4 mobs need to die.
On the other hand:
*the loot is nowhere near on par with what you'll get from a heroic dungeon crawl.
*if you don't "finish" the quest line in Splitpaw, you'll constantly be reminded of it whenever you finish another quest...as your journal will automatically switch to the "I need to find out what is happening to the Splitpaw Gnolls." 