I play a lot of immobile mages, particularly
. What's immobile mage 101 for when someone jumps on your face? Stun them, if your spells are fast fire them, then run away as fast as you can.
Camille's ult makes her untargetable while she's starting it, which is usually right at the "ok, this person is too close for comfort, stun them" point, meaning the stun wiffs. That's something that can be overcome with practice in the matchup, but it's annoying none the less.
Then there's the fact that you can't runaway (part 2 of immobile mage 101). You saved your summoner spells to be able to get away when things went from bad to worse, but Camille's ult negates that possibility. Flashing to the other side of her isn't helpful, you're still in melee range with every spell you have on cooldown.
"But Positioning! Where are your teammates!"
I'm
, I'm on the far back line so I can get my ult off. My teammates are on the front line or just behind the front line. Me being in position is me also being out of position as far as Camille is concerned.
Xerath's stun is 0.5 seconds at point blank range, which is basically worthless when I've got to survive a 4 second cage fight. Even if I zhonyas after the stun wears off I've still got a second left for this Camille to tear my face off, during which time she's going to have a magic damage shield up. Should I survive that cage fight, there's a good chance she'll have her slow+movement speed boost up shortly or she'll have her hookshot+stun available. Depending on how the rest of the fight went, my teammates are either chasing down kills on the rest of the team or retreating with their tails between their leg.
So... yeah. Camille's just miserable to play against for someone in my position. That's how she's designed. Yes, divers are counters to immobile mages, but Camille feels particularly oppressive, even by diver standards.