Ok, so the community is currently split on Vlad - some people say that he's OP, some say that he's UP. I'd like to offer some analysis on this phenomenon. (I know that downvotes and upvotes for this thread will come from both parties, but I will try to be as factual as possible.)
- Vlad has a poor early game.
- Vlad can be shut down early.
- Vlad, when shut down early, is not a threat.
- If Vlad has a good early game, he is a very large threat.
- It requires a specific working knowledge of Vlad to shut him down early.
From these facts we can garner an analysis:
High-level or experienced players have both the knowledge and the skill to shut Vlad down in his early game. Therefore, one who plays Vlad against these players will complain about him being underpowered.
Lower level players or those who haven't played against Vlad often do not have the knowledge to be able to defeat Vlad in the laning phase. Therefore, he hits his peak quickly and starts ripping apart his enemies. These players will complain about Vlad being overpowered.
In conclusion: Vladimir's play is nearly as binary as the play of stealth champions. As you have acknowledged this and are proceeding with a re-work of stealth and those champions who use it, I strongly suggest you look into Vladimir.