Hard mode is a gimmick - Yes but nowhere near what DoA is. I've done alot of hardmode missions so far, all on my mesmer, and have always found that I can contribute alot to a party. In DoA I can only contribute if I take the most overpowered pve skill in the game and build around that. That you need mostly human players is good imo, though indeed in the 8 player areas the players are a little thin, but isn't that what guilds and friendslists are for? I am sure you can find other dedicated Hardmode players if you look.
Assist other thru normal mode - If you enjoy doing that, why not? I don't, I help guildies and friends when I'm free, but I don't go looking for this.
Start another character - You've tried starting an ele and got a ritualist and ranger. Well, If you want to compare to the power of an SS necromancer, the ele would come closest, but needs skills from all over the place. With well placed aggro Ele's even outdamage SS necromancers because of the added shutdown from MS (the DoA way). An ele also makes excellent support and therefor a welcome addition to any hardmode party for instance. And if anything is truely difficult there is always place for an ele, whereas as soon as a second necromancer comes round he is doomed to BiP, look at DoA, The Deep and Tombs (before B/P). Someone else already mentioned that playing a warrior plays entirely different and it does. A warrior typically makes or break a party and is naturally looked apon to lead a party. I won't try to make you play a mesmer, it only suits those who do not care for direct power but want to supplement a party as best as they. With the lesser powerful elites and powerful skills if used wisely it is doable for a mesmer to take a cross-profession elite. Assassins are a joy to play, and add alot if played well. Paragon is nerfed, but still builds exist that will make everything just this bit easier, not the most exciting builds though. Wouldnt recommend dervish until you tried a warrior and stay away from monking.
I don't think individual effect is minimised. When I look at it from my view of grouping for a tough mission the following professions are the most wanted and the one player skill matters most.
1 - Tank - He is key. He needs to either have done it before or he needs to be able to listen very well. Titles on tanks (triple prot, explorer, skillhunter) impress me and make me take them over other players.
2 - Elementalist - I need nuking, but I need it rightly applied. Yes nice meteor shower on the melee, but now they will break aggro and the monk there will heal them anyways. No don't attack the next group, let the tank take aggro. Wtf firestorm. You get the idea.
Then if it is not DoA.
3 - Support - Barrage ranger with distracting shot/savage shot/dust trap, Domination mesmer, illusion mesmer, paragon, ritualist. The people who play these roles I will have to know, or I'll play it myself. If not able to bring one, I'll bring an extra nuker.
And lastly, monks and necros. I'll admit that SS is overpowered, but that basically leads to a very one-dimensional class. Necros are a dime a dozen. Every one of them has a SS skillbar and has played it before. C + space + Reckles haste + SS = gg half of the time, the other half you casted SS on a caster, but most figure out we want other targets after some encouragement. For Hard Mode Minion masters are nice, but from building a party point of view no concern, a Hero does it just as well, for the other stuff minion masters are too weak. Monks are also plenty, though you need real ones for Hardmode and elite stuff, they are typically widely available.
Farm for FoW - Or farm for tormented staff, a mallyx mini-pet, whatever.
PvP - Or TA for glad points

But if it doesn't suit you, it doesn't.
You've forgot:
-Master The Deep/DoA and lead other groups through there.
I would advice you to start another character. Go for ele or warrior. The experience is completely different and like I said before ele's can always get into high-end pvp groups, warriors too, but if you don't know what you are doing you will build up a bad reputation and then it will get hard to find good groups, until you show otherwise.