The dodge movement is again for early game ganks, if I'm going in for a kill my runes + masteries usually allow me to dodge attacks from the minions when I'm going near his turret making it easier for me to finish him off, but to be fair I didn't really change the masteries when I gave up Phantom Dancer.
Spirit Visage is something I usually take when I'm having a hard time at the start with no income, but I didn't want to post the build I use when I'm failing, if I get the headstart I usually do I don't need more health regen, I benefit more from the items I listed.

This is the build I use when I'm playing with my friends, preorganized team that counts on surrender/victory hopefully before lvl 18. When I play solo I often end up with the Visage and change my build a little due to lower income.

I checked your build and liked it but it's just too slow for me. But I thank you for you comments and now I know what I must add to my next build, but again, this is the build I use when everything works out since it usually does.

You can argue your build which is a good thing to be able to do. Have you considered Spirit Visage, it basically boosts Mundo's Ult into a major force to be reckoned with.

+1, I hope you expand upon your descriptions as time goes on.

EDIT: Also another thing I've picked up on is the dodge movement speed boost. Seeing as you have no items to support this and only one set of 9 runes do you think you should either change the masteries/items or runes? Just a thought

The reason I didn't pick a full mastery tree is because I'm mostly counting on it early game and I think these are the best stats I can get for that matter. The hp helps alot since I don't pick Doran's first, but I'm in no need of attack speed/ability power and 4% damage reduction doesn't seem worth the 4 points to get to it. Then I just go for the Cooldown reduction and the most dps I can get out of it.

To the Warmogs case, I know I get it a bit too late, but the problem with it is that even though you have it you are still taking full damage, and HP isn't going to help you survive if you have no armor/magic resist, I do buy it sooner against tank heavy teams though.

Thanks for your comment, buying Warmogs before I get Sunfire / Thornmail could make a difference.

Interesting about your mastery selection is there a main reason you decide not to fill a tree? Also don't you think you get Warmogs too late to gain it's full benefits? Have a read of my build and tell me what you think. I try to explain as much as I can.
Good start btw. When you have commented back I'll give you a +1 to help you on your way.