You have to ask what the publisher is going to do for their cut. For me, there's four circumstances which would make me say that a publisher might be worthwhile:

1. The publisher is funding the development
2. The publisher has a very good marketing pedigree and a lot of clout (e.g. Rovio Allstars) and your app is a particularly good fit with their user base so they're pretty much guaranteed to generate a lot of extra income
3. You have some reason that you can't do marketing/publishing by yourself (e.g. maybe you don't speak English, or maybe you're from a country with problematic iTunes/banking systems, or maybe you are incapable of communicating with people without riling them up)
4. You're fully embracing f2p mechanics and you have data showing that your game can get to a point where the revenue per user is greater than the cost of user acquisition. In this sort of scenario, a publisher might be worthwhile in terms of helping you optimise your KPIs and providing and managing the very large advertising budgets that will be involved in exploiting the money printing machine you created.

I think for most developers, especially indies, none of these are usually the case, and the best choice is self publishing. Otherwise I think you'll just be giving a big percent to a publisher who really has no incentive to do anything much to push your game, from their point of view, your app is just a lottery ticket they got for free.

Not that I can claim to have had any great financial success with my indie game :). We have had reviews and Apple features without a publisher though.