A lot of Vladimir use it.
You can use it on Illaoi against certain team comps.
Some confident Assassin mains pick it over Thunderlord's.
An alternative could be: Your spells and abilities against enemy champions apply stacks of Stormfront. At two stacks, your next basic attack against that target shields you for a little bit and grants you a Lightning Cloak for a few seconds that deals magic damage to nearby enemies. 30 second cooldown.
It would be similar to the Storm Shield of Dominion. You could trick enemy champions into fighting you when you're low Health this way. Or you could win extended trades more easily when it's up. The cooldown would have to be long enough for that, though.
Ranged champions get the shield more easily but can't make any use of damage passive. Melee champions have a harder time getting the shield but can make use of the damage when they do.
You would pick Thunderlord's over this when you want more poke and burst damage. Also, Thunderlord's scales with Attack Damage and Ability Power and this wouldn't.
It would still be good on Vladimir and Rengar (as he doesn't have a great escape ability), but it would be accessible to more champions.