While it is true that you should aim for as few polygons as possible, if you just have a “hero” character, you could get away with a high-poly model.
That being said, if your 3d modeling and mojo is up to it, any 3d suite that can export to fbx can make ue4-friendly characters.
Programs such as Poser, iclone, and Daz are technically not really character creators, but rather character modifiers, in that they depend on pre-made content which you then customize and animate. They take away a layer of complexity, but doing that reduce the amount of low-level detail and tweakability you could otherwise have. I believe this is the case with makehuman, but I am not 100% sure.
My experience with this kind of programs is, and mind you, it is my experience, so it surely is unintentionally biased (so please don’t let’s start a flame war):
iClone being a sort-of machinima render engine, has quite a lot of models with low polycounts. Coupled with the pro version and 3dxchange pipeline, it can output fbx files of characters that have been licensed to be exportable (and not all iClone characters are, just so you know). Importing you own mesh and rigging it is actually not done in iClone but in 3dxchange. If you’re not doing terribly complex stuff, it is straightforward enough.
Poser, or rather Poser Pro, can output ue4-ready files. On export you choose whether to export as a static mesh or an animation, whether to force textures to be a power of 2, etc. Quite straightforward. The only thing to mention is that if the figure has lots of nodes in it’s materials, the exporter can have a hard time on deciding just how the material should look. As materials (or shaders rather) are usually tweaked after import, this is usually not a hassle. While you can export pretty much anything you have in a Poser scene, some Poser assets are not licensed for use in game engines etc.
Daz Studio… I have tried to use it but I always come back to Poser. It is just wired a way that makes my head hurt. Poser does all the thingies I need, so I don’t really have a use for Daz Studio anyway…
For the long run, I would encourage you to learn a 3d modeling app. And a character rigging/animator app. Which can be the same app, or something like Poser, Daz Studio, Messiah, motionbuilder, endorphin etc.
Anyway you choose, just make sure that ANY asset you do not create yourself, you are actually licensed to use as you see fit.