Just to clarify and add a bit to your post tyriien.......

Some damage dealers are just fine and are 10x more powerful and potent than any tank or healer.  (necromancer)  My necro can kill/kite 4 dot mobs 1-2 lvls above me in a moderate to long amount of time.  4 dots below my lvl take about as long as 3 dots do for say a ranger.  just for clarification not all damage dealers are having a tough time.

Also clarification, with the exception of the extremely well equipped tanks and paladins because they can heal, i do not think tanks solo well at all.  No better than a well equipped monk would.  If they go 2handing they lose a lot of defense and even some of their shield attacks and if its not a paladin that can pose many potential dangers.  The shield plus 1hander combo for tanks on AVERAGE i'd say would allow them to possibly solo 3 dot mobs a lvl or 2 underneath them, maybe an even con at best.  I can't see a tank being able to kill quickly enough to offset the damage done by the mobs unless he is wielding very powerful weapons and very powerful armor, which i'd wager the majority of tanks do not have.

As for healers, i'd stack most of them with the tanks ability to solo on this one, unless they also ahve fantastic weapons/gear.  Cleric with a 2hander and focus on str will probably kill at a nice moderate pace, and stay alive easily as long as his heals aren't consistently interrupted.  Shaman can get a pet to tank kind of, blood mage can sort of nuke but they are paper and prone to dropping quickly, and disciple has had huge DPS nerfs so im not sure they even stand with clerics at this point. 

I think you exagerrated a few numbers perhaps to keep your opinion convincing, but i dont think the typical cleric can solo 5 even con mobs, even 2 dots.  Thats too much interrupts on the healing spells against a low DPS class who doesn't have outstanding defensive prowess (aside from heavy armor).  I've seen clerics drop as fast as casters on a regular basis.

I've seen plenty of rangers soloing like it was cake, i've soloed like cake with both my druid and necromancer, i've soloed with my shaman it was slow going, i've soloed with my monk and sometimes it's fast because the crits pop up often but usually it sucks and i avoid it.

As far as "leaders" go, you do need a healer, you do need a damage taker, thats just a given in how these games are played i guess (and i'm all for changing that).  However you may find yourself also needing CC and i wouldn't consider DPS classes a minor role.  I think a DPS can be a "leader".  Some DPS classes do and should have tanking potential  (currently the ranger too much the monk not enough). 

I don't think you should perceive the clerics and healers and tanks as being some fantastic way more powerful than ours class.  I have beaten even lvl warriors in duels, one even had most of his MoP armor and a nasty 44DPS axe.  I've defeated a dreadknight with a 50ish+ DPS 2hander.  Even when they go shield 1hander their damage is so subpar i've come out on top.  I've defeated a cleric very very easily.  He may have heavy armor but it makes no real difference, i blasted him with thousand fists with my 2hander and he was dead in about 5 seconds.  I've also bested rogues (and they have bested me before also, damn stuns). 

My point is this, we are not as weak as you are making us sound, and the classes you are perceiving as powerful are not THAT fantastic.  Perhaps the people you have witnessed doing these crazy feats were good players who were very well geared, probably a part of some powerful guild. 

As i grow in lvl my monk seems to grow greatly in strength.  Im harmonious so i hear we are the closest stance to being fixed so that might be part of it, but whereas i used to feel weak and insignificant compared to other classes i am starting to feel like a true force to be reckoned with in the DPS and fighting ability area.  Yes i do have some bugs that need to be adjusted, and skills that could be better, but i can still pwn with him the way it is now and if he ever gets fixed.....well, we'll just wait and see.

Ryoko didn't type much up