It can be.
Most don't recommend it for obvious reasons (No Dark Pact, not as much healing returned via spells), but don't let it dissuade you.
I leveled 1-70 as Affliction and then respecced to Destruction and I love it.
It's a "Shadow Mage" style, for sure, but if played right (with average to above average gear), you'll have very little downtime. I use the VW and I rarely have to stop.
Give it shot - you can always respec back (or dual spec). :)
That depends on personal play style, whether you like PvP, or PvE, and whether you like tanking or dps'ing in PvE. Arms is good for pVp, and PvE has fury for it's best dps spec, but the tank spec should only be picked if you like Tanking in PvE.
For 3.3.3 destruction tree's are very easy you can check out my build i pull 8k DPS in ICC. See Talent Tree in Related Links 3/13/55 is the PvE Spec. The other talent tree is PvP destruction.
Each class is good at certain things and bad at others. For example, hunters make terrible healers, and warlocks make terrible tanks. It also depends if you mean PvE or PvP. What talent tree you pick has a big effect on situational effectiveness, too.
Playing on a PVE server myself, i feel that Aszune is quite active. It all depends. Try some different PVE servers out and find the one which you most prefer. Its all trial and error.
yes because they can heal and attack
The Horde have 3 races which can become Warlocks: Orcs, Forsaken and Blood Elves. In the next expansion, Cataclysm, Goblins are also able to become Warlocks. Which race you choose depends on your playstyle and preferences, there's no real "winner" in this. The Forsaken have the advantage that they can consume corpses to regain health and have Will of the Forsaken, allowing them to get rid of mind-affecting abilities that would stop them. Forsaken are considered to be very good in PvP combat. Blood Elves can Silence their opponents, which comes in handy against caster mobs and enemy players alike. This is also a little more handy in PvP than PvE combat. Orcs have the benefit of being able to empower their pets, making Orc Demonologists quite powerful. Orc Warlocks are more all-round, good for both PvE and PvP, but since their strength lies in their pet, you will get the most out of it as a Demonology-specced Warlock. In the end, it depends which race appeals best to you. Choose wisely, because you will be playing this character for a long time, so it may be best to choose based on what you'd like to see your character as, rather than just power.
i would recomend: thottbot.com wowhead.com and be.imba.hu if you are into pve
Depends on what your trying to do. Blood Magic is good for most PvP and some PvE, but it tired to target mostly one person. Curses can be both PvP and PvE by snaring one person or multiple people with elite spells like Spiteful Spirit. Death Magic is mostly PvE because of Minion Mastering.
Mages are more dmg with spells and stuff but druids are genrelly strong if they are feral spec and attack in cat form. Depends on how smart and geared each of them is. Also depends on what specs each of them are and if they spec'd for pvp or pve.
depends on your spec and purpose pvp ambush will need a slow dagger in the main hand but a assassination would like some faster ones pve (raid) combat will like the slowest possible dagger for the windfury proc
Player vs. Environment
No. You can flag yourself for PVP play on a PVE server. Though it is my experience that most people don't flag themselves for PVP on PVE servers in DCUO.