Every build in the game works.
Pros - Dark is very powerful, Elec gives extra control to what is already a very controllery primary, the Nuke on elec is awesome.
Cons - There's little synergy besides a doubled-up hold, elec is pretty low damage. Your sig says you already have a kin/elec, and variety is the spice of life.
DON'T eat muffins while I'm developing you.
Pants! Turkey Magnates! A man in a box! Rogue AI! Come one, come all, to arc ID 10107 - It's [i]'Not as long as some other arcs'[/i]!
I have a Dark/Elec and yes, it does work. However, if you do decide to roll one the main thing you will notice is that you will be trading off damage for control. I simply cannot solo mine at all and he is very team dependent. Certainly good on a team but useless outside of one. The other thing to notice is that the endurance drain effect of the secondary on its own is not enough to prove effective. Unless you couple it with Power Sink from the Epics, draining a foes endurance is next to useless as an attack. In more prolonged fights it can be ok but otherwise, meh.
The two holds do stack which is nice and you do get two pets which certainly helps matters but it depends on what you like to do. If you can cope with the poor damage output and team dependency, you will be very useful on a team. Solo though, you will struggle.
Hope that helps. 
@Dante EU - Union Roleplayer and Altisis Victim
The Militia: Union RP Supergroup - www.themilitia.org.uk
AS the title says does it work and what are the pros and cons of it
Is not going to remain VIP after Jan 14th 2012, but may remain an active Premium account holder.
See some of you guys/gals in other/new MMOs Soon(tm)
N.B. If you are going to do smt, please do it or GTFO and STFU nab