Being a newer Viktor player, my only problem w/ him has to do w/ his end game viability.
The one nice thing about Viktor is that his augments allow him to play a variety of roles on his team, and in theory, all of it works out, but in practice, he really falls off when trying to make him play a support, he just cannot bring as much to the table as a true support can. The way I can see this being fixed is with another build path with his Hex Core (Tier 3 upgrade that is).
How I propose this works, is take his Augment Gravity: Gives 30% range on his stun, 200mana, 10%CRD and 5mana regen. So, if you were a support, this will help you set up for your team to come in, and if you added a tier 3 to it, I would say adding something along the lines (a little bit of everything, just 1 of the following, or if somebody has a better idea)
5 to 10% MS increase for allies running through gravity field
Small MR/Armor aura when its on the field or a flat amount in an aura (~750 Range) per champion it hits to surrounding allies
Possibly an activate on hexcore that gives a small boost to a stat, or a limited heal, w/ a 60-90second cooldown
Augment power adds movement speed to power transfer, 220hp, 6Hp regen. Another tier could add
Bonus MR/AR after landing Q
Aura that increases allied champions speed after it hits possibly (~450-650 aura range) for 3 seconds
Possibly a lifesteal on the Power transfer, but would be for 1/4 - 1/2 amount you get shielded)
Augment death gives 30% burn on Laser over 4 seconds & 45AP. Putting a tier 3 on it would give:
5 to 10% inc. AP to Viktor only, or maybe an activate that lasts 10 seconds w/ a 2 minute cooldown
Flat Magic Pen for 5 to 10 seconds after you land an ability on an enemy champion (champion, not minion, if it was minion, it could be used too much and kept on almost all the time)
Again, these are just some ideas to help improve what role you want Viktor to be in, and also give some umphf to his Late game, I would love feedback on these ideas.