Valkrionn
The Hamster King
Or if their units became maintenance free after winning combat. 

Apart from lacking libraries her economy is just as strong as any other non-financial leader.
Organised, charismatic, expansive, creative, philosophical etc all give other bonuses that effectively boost your economy far more than a saving on a couple of training yards and a mage guild. The lack of libraries does give you a noticable slowdown in tech. The big bonus from building military units without a required building is actually the speed you can militarize, but that's only useful if you have the economy to support a military campaign. This is where the Doviello really fail, whatever they conquer just drags their economy to a standstill.
Now try doing that with Hippus.People are always underestimating the Doviello. The first thing I always do after downloading a modmod that changes them is to look how fast I can conquer the whole world on a standard pangea map on immortal. I never need more than 200 turns if I play base FFH, FF, Orbis or in Wildmana. You just have to be willing to start wars ASAP and to bash your opponent with your starting units. It's simple, oldfashioned, straitforward - certainly nothing flashy (but that is another point that has nothing to do with their power). Sometimes you want just to take your axe and slaughter through your opponents without being obliged to go for more than bronzeworking and the base economical buildings.
Sure the Hippus are very strong and on the long run probably stronger (as they are among the best civs in the game). But that does not mean Doviello aren't strong either. I never meant to say that they are the strongest civ, but that they aren't that weak as some people assert.
I always feel so inferior when the Doviello approach me offering to trade Writing for one of my techs. It's like really, you guys figured out how to write before us? What are my sages doing with my money???
It's not just the Hippus. I've done similar conquest runs with Svartalfar, The Clan, Luchuirp/Mercurians, Sheaim and Khazad. That's a lot of competition for the Doviello. Outside of early conquest, the Khazad have a stronger economy, Sheaim stronger magic, Svartalfar and Hippus have stronger units and the Luchuirp/Mercurians have the largest army(You could say the same about any civ and the Mercurians, but the Luchuirp can summon them the fastest, hands-down).
The point is while the Doviello might be okay, they really don't excel in any one area. They don't have a unique bonus that is fun to play around with. In fact, they are about as close to a vanilla BTS civilization as you can get.
Right. I don't think that any civ except the Hippus (with their worldspell) is able to lead and win war until turn 10-15. After that Lucian is so strong that he can easily kill any civilization.