I have the Power epic... and I don't think that the shields are especially necessary. A nice addon, but really not needed. My Kin defender can easily heal back any damage (as can Dark), so it was a bit of a silly choice for me to take it.
Most of the time I don't use it, to be honest. Take a shield if there's nothing better available at the time, it'll be useful, but you won't miss out by not having one.
Go with Elec Epic and revel with Power Sink!
A single target immob (I found it usefull, many others disagree 
, the 'decent' armour due to its inclusion of energy, thunderous blast - a pretty deadly melee move and the already mentioned power sink.
Dark Consumption has a _very_ long recharge, even with x3 recharge reduction + hasten ect (6 mins base I think?).
But either Power or Dark? Power all the way ...
I've gone for dark mostly for concept.
I find the armour very useful, and combined with shadowfall, gives you some very reasonable resistance numbers. Also, with an all black costume and blue starburst eyes, the SF/armour combo makes you look a bit like a Dark Servant, which has comedy value (an underrated factor in power selection imo).
Soul Drain is a whole bunch of awsome wrapped up in a bundle of fantastic. Three recharges and it will be up most if not all fights.
Dark consumption has, as mentioned earlier, a very long recharge. I've found it most use as a post nuke recovery power.
The health for disorient thing I've only tried on test. The health drain was negligable, but the disorient was too.
Dead Calm's Defender Manifesto
I was comparing dark consumption with conserve power (as they are both a way of recovering/managing end) and according to my figure CP had double the recharge time as DC, so taking that into consideration DC doesn't seem that bad.
Wasn't even considering taking OG, just because I can lock things down with fearsome stare or petrifying gaze, so can't really see a situation were'd I'd need a mass disorient. I do like darkest night herding for nuking so the dark shield does should like it'd come in useful (I think I'm right in saying it resists more types of dmg than temp inv).
So still can't decide.. I am leaning towards dark now, for concept aswell as usefulness for what I want. Guess I'll have to try out the test server and see 
Thanks for the replys all
ive found CE very useful, when RA runs out got CE for back up to help rest of team etc...
Well I'm slowly reaching lvl 50 and just wondering if someone could give me advice on epic powers.
But does anyone have any useful information, advice, previous experinance with both?
Now my main power sets are dark/dark and from where I want to go with Tufty I've decided that either Power or Dark mastery would suit. But can't really decide which (although I did select Power Mastery at lvl 41 but I have 2 unused respecs I can use).
The main reasons why I've decided to take either power or dark are 1) I'm a very offenderish player. I like to blast away and do some damage. Because of this it seems that either power build-up or soul drain would help in increasing my damage output. I'm guessing that soul drain is similar to a kinetics fulcrum shift, any one have any idea what kind of extra dmg you can get from it? Power Build Up seems useful because, unlike soul drain you don't need to be surrounded by enemies and it enhances more than damage, downside is it has double to recharge time and doesn't last very long.
Becuase my play style involves alot of jabbing buttons I do sometimes find myself running low on end, especially when soloing. By taking either power or dark mastery, conserve power/dark consumption would help with this. As with build up, good thing about conserve power is you don't need to be surrounded by enemies for it to be effective but it has a very long recharge time compared to dark consumption, which in order to fully benefit from you need alot of enemies near.
So thats basically it. At the moment I'm trying out power mastery although I'm very tempted now to switch to dark mastery. I enjoy being in the middle of the battles so having enough enemies around to make the powers useful shouldn't be a problem and its also better for concept reasons
Another question I've got is how essential are the epic shields (3rd tier powers) or the epic pools. Is it advisable to get one or can it be avoided?