I have always felt that the more defense you add to a build, the less offense you can have in a build. I want to have my damage champions doing a lot of damage, not just surviving long enough to get out while their spells do very little damage.
I've always found that I can easily survive mid game with use of wards and keeping a team mate around if I'm going to be leaving the lane. In a team fight about mid game, I've found people focus the AD carry a lot more often than Viktor so until you start taking some serious damage, you don't even need to back off.
Late game is when people are going around hunting individuals so the rylai's OR RoA helps here the most. Being able to survive that initial burst long enough for them to be slowed/stunned by your W and getting out. If you do plan on going RoA, get it early enough that the over time stuff will cap out before its too late (by minute 20 is when most people get it)

Oh nevermind.

Man, you got 6 items, did you forget about the hexcore?

Sounds interesting, i ll probably try it. and i like how u have a specific item for a specific augmentation. thats smart. i've been trying out a more tanky build tho, with Armor runes, and it has been ok. some games i go positive 3 or 4 kills, however other games i go negative 5 or 6. i know part of it might be my skill playing, im lv 25. but i still wonder about the build. how come u added pretty much no defence other than tons of HP at the end, and how do u deal with mid game stron characters, if u have low defense? i know W is sort of defensive but ppl get arround that sometimes, specially AP ranged players.

Anyways, thanks for the build, ill try it out.