All the faction aren't bad, until they GET power. By reducing the patrician early we could have retained a lot of wealth used for larger projects.
Just think how much money that Redshore smuggling/spy network run by the governors must have stolen over the years. Then times that by how many families just as old this civilisation must have.
It would also have enabled more social change, after all established power/wealth resists change.
It isn't the amount of power that a faction has that matters, it's the balance between the factions that matters. The guilds can counter the Particians to an extent, and the other factions working together can do the same. It's only when we have a faction with power concentrated in it that we get problems.
Also, you're misunderstanding the role of the Particians. They aren't stealing our wealth with their power, they just push for their own personal projects to get finished. Hammering them down does nothing but make more trouble for us, unless they are legitimately doing something dangerous.
And what social change could we have gotten by hammering down the Particians? There must
always be a ruling class, so even if we crushed the current class, another of the factions would just replace them. We have WoAN that if we did, for some reason, decide to crush our current Particians, the next strongest faction would be renamed to Particians and gain the same powers as them.
Not to mention we've spent quite a lot of effort cultivating our traits to have a competent Partician class, so crushing them makes no sense.
Edit: It should also be noted that keeping the factions weak does make it easier to control them, but we also lose out on
significant benefits if we do so. Urban Poor can increase our Legitimacy cap, Traders can increase our innovation rolls, Particians can suppress rebellious factions or support useful ones (like they did during the Horseman's plague), and so forth. Keeping them weak means we can't benefit from those powers.