Thank you all for nice and informative replies.
We decided to stay on our path to SHs. As some of you mentioned there might be less fun for one of us playing SE.
We are progressing through DE starter lands and planning to go check areas around Gludin and Dion.
So far so good ... Couple of deaths here and there when trying to master ping-pong and the usual where do we get more adena but we're enjoying it anyways.
I have a 76 Stormscreamer as my main. I do a lot of pvp and a DE mage is fun, but you are primarily a debuffer then kill type nuker, rather than a straight up pound down damage. In other words 1v1 vs a sps or sorc you will not be able to keep up becuase you cast so much slower. So if you are going to be into pvp at higher levels roll a spellsinger. I sometimes wish that I chose a sps early on, but I like the unique abilities of the DE nuker.
For raiding and PVE the spellhowler is the best nuker hands down.
For leveling always use your shadowspark/flare spell to end since you can get nice overhits (extra XP) for every kill. Some people complain that you get extra XP and dont get extra Sp so you get SP starved as you level, but just get the levels you'll get the SP you need, its ridiculous to turn down extra XP.
One good way to level later on is with the curse death link spell. You have to get as low as you can get in hit points to really get the power out of the spell. Keep casting body to mind until you can't cast it anymore because you are so low in HP and use CDL. You can one hit mobs even at higher levels.
If you are not CDLing you still always want to use body to mind at least once for evey nuke. Then you use vamp claw or corpse drain to get your hp back up. If you use body to mind consistantly, you will never run out of mana.
As far as spots to level, there have been to many changes for me to tell you a good spot. It all depends on gear and buffs though. And half the fun is finding areas on your own and exploring. So just go out there.
As far as duoing, if you duo with another nuker, assign one person to pick targets. The other person should assist the targeter, and not try to select the mob. In other words use the assist command or right click the targeter's name in the party list. This will ensure you stay on the same mobs or dono't pull different mobs at the same time.
As far as duoing, having an SE is the best help. Empower is essential once you get past 30. The SE will be busy recharging, you can also get into 2x or 4x mobs areas and have the SE root while the nuker nukes. I know several live SE's and they enjoy the class. But one way or another you will need the buffs.
Another good duo that is fun is the bladedancer/nuker duo. Once the baldedancer gets dance of mystic and concentration the nuker damage output rises. Its hard for the BD to keep up with the nuker, but if you use the BD to bring in extra mobs it works quite nicely.