Wiz epic is sorta lackluster. If you're looking at items as hard to get as an epic, you also have to consider every other option.
The wiz epic replicates the effect (plus a minor boost) of the spell manaskin for 0 mana and 0 reagents. That's not nothing, but it's also not a ton.
You can't really look at the clicky as a boost to mana regen (ie assuming you combine it with a mana stone or manna robe). It's more dps and less work clicking to just pickup a Rend robe, a Hoshkar staff, or a Velk robe.
As a free rune on AE fights - it does have some minor use. It's worthless for the most part in Kunark because most raid mobs die before it eats through your manaskin+manaskin combo. In velious, it has some more use. A well adjusted wizard can likely mana-dump on an AE mob fast enough to not take significant damage from any AE's before ducking behind a wall. It's sole major use is re-runing during breaks hiding behind a wall. That isn't horrid, but hey, diamond wands rot also, so it's not quite as good as it could be.
As far as stats, the wiz epic disappoints. It's good for pure mana fights, but not game-changing. If the mob has a MR, PR, or FR/CR AE, then you're going to instead be using a phinny staff or a staff of gabstik. In fact, the wiz epic is the only epic, where the items you turnin, add up to better stats than the final epic.
TL
[You must be logged in to view images. Log in or Register.]R - The wiz epic is nice, but it's hardly game changing. A mana-free rune is useful, but is not class defining or game changing. There's a reason it's ~#3 on my Kunark wish list behind 2 other clickies.
Also, just wanted to put out that Rangers are probably the most lucky melee class in terms of epic. They get the major advantages of the rogue epic in the offhand, in the mainhand they get another great weapon with a slow/agro proc. Additionally, they get the effect of the monk epic in a friggin PoSky cloak. It's a great raid epic for them and a phenominal solo epic.