The XP found in the Heroic quests continues to be the low XP that the Devs have given us. I would expect that the XP would be better than what the current "placeholders" are for two reasons.
Firstly, the Devs are pushing awfully hard to skip Eberron content and go directly into Forgotten Realms. You can see this with the creation of the new Iconic Heroes. It also seems to stem from many newer players and some older players that prefer Forgotten Realm's traditional fantasy over Eberron's post-apocalyptic steampunk fantasy.
Secondly, since these quests are part of an Expansion, there should be something "special" about the expansion. I've mentioned elsewhere that there doesn't seem to be anything noteworthy in this expansion so far. The loot is absolutely horrible, as can be attested by every comment about the loot. There's no raid. I've mentioned elsewhere the lack of a new campaign setting and the underused and/or unused new environmental effects that were presented in Shadow of a Doubt. So that pretty much leaves that the XP should be the standout point of the Expansion, which costs more than a regular adventure pack and also treat differently than an adventure pack.
These are the numbers currently for the XP in the Heroic quests:
* 1670/3016/3133/3250 - The Thrill of the Hunt
* 2308/4173/4336/4499 - Army of Shadow
* 2452/4433/4606/4780 - A Lesson in Deception
* 3169/5733/5958/6184 - Friends in Low Places
* 3408/6166/6409/6652 - Through a Mirror Darkly
These numbers should really be closer to the numbers found in the flagging quest in the Vale, in my opinion. The XP in the Elite flagging quests in the Vale are between 7299 XP and 10,036 XP. Vale also contains multiple wilderness maps, 3 raids and a crafting system that is still viable. Buying Vale from the DDOStore is 850 TP, while the basic pack for Shadowfell will cost 2495 TP.
Now out of all these quests, I think Through a Mirror Darkly has the strongest argument for needing more XP. Besides having a confusing map that might lead to players continually backtracking through the same areas trying to find the orbs, the new mechanic alone justifies an increase in XP. The optional boss (if no one in the party has instant kill) and the end boss can extend the quest much longer than is needed, especially if soloing. The quest is sort of a combination of Inferno and Shadow Crypt with an extended end fight. I also foresee this quest not being very popular with many people (even though I personally think it's the best quest so far in the expansion). For all these reasons, I don't think it's unreasonable that Through the Mirror Darkly should have heroic XP similar to Coalescence Chamber (5359/9300/9688/10,036) or Shadow Crypt (5568/9820/10,360/10,900).
Stormhorn quests appear to have Heroic options also. The Heroic quests are level 19, so the Hard difficulty is level 20 and Elite difficulty is level 21. So once again, these quests are competing with Epic XP at level.
The following are the XP amounts in the Stormhorn quests on Heroic, for the quests that I've been able to find so far:
* 1984/3553/3676/3800 - Breaking the Ranks
* 2295/4113/4256/4400 - The Tracker's Trap
* 2348/4206/4353/4500 - Lines of Supply
* 3737/6700/6936/7172 - A Break in the Ice