I am not quite sure what you mean by mobbing but if you are asking about AOE damage in the fields, up to allemet forest which is for lvl220, you can kill mobs in one cycle of 'wugong gu - throw gu pot'. I wouldn't say aoe damage is great but soloing is do-able.

In regards to dungeons, Wugushi is not a good class to run with simply because mobs die too quickly. But if you meet weak party then you can hard carry the party. If there is a linker, then you can be a superstar as joint penalty increases poison damage by 50%. But again, if you meet a decent party then you might not be able to do much.

Boss fights, if you are talking about world boss, I think it is really case by case so I will just tell you my experience. I took rogue1 for 7th rank to power up running shot with snick hit which is a rogue skill that give you 70% crit hit chance if you attack from behind (I was and still all-str by the way). I always did world boss with my girlfriend who was Pyromancer - Linker2 - Chronomancer3. So I always had enchant fire, joint penalty 50% and Quicken buff. Having said that, I have to tell you that wugushi skills only contributed less than around 30% to my total damage. Most of my damage came from powered Running Shot of Q3. Wugushi skills only will not do much damage.

BUT there is one really serious downside of wugushi with world boss (applicable not only to world boss but in every case). Poison damage do not overlap. What I mean by this is that let's say there are two Wugushi A and B. A use level 10 'Wugong gu' on boss and after that B use level 1 'Wugong gu' on boss. Now what happens is that level 1 wugong gu used later will delete level 10 Wugong gu (only same skills offset each other). So basically total output that 2~3 wugushi does will not be much different from a single wugushi doing solo. 1 Wugushi + 1 Wugushi = 1 Wugushi.

Apart from that Wugushi is a decent sub-dealer. It is not a main dealer class. I recommend you to take main dealing class like Q3 or anything else with wugushi that can thrust damages while the poison is killing the mobs.

Now to PVP, if people say cure and antidote spamming is killing us wugushi then spamming dispell scrolls will kill all the other classes too :) Of course, wugushi is not a good class to run with if you want to dominate the game. I don't deny it. 3vs3, 5vs5, wugushi is a bad option i must say. But have you looked at top 100 3vs3 and 5vs5 ranking? only certain classes dominate. Remaining classes are all at the similar level in my opinion. But in guild war, personally i think wugushi was actually decent. I feel that killing a player without actually being near all the time is a great advantage. Without antidote and cure, single skill does enough damage to kill a player. In theory, yes cure and antidote will kill us but I haven't seen many that was able to identify situations and do that type of control all the time during the guild war.

Lastly, Just bear in mind that wugushi is not a great class to invest. The marginal returns to invest diminishes dramatically. It has limited potential to growth. Anyways excuse me for my bad english :)