I would vote Defender Titan. Then again, I also despise the Warlock jump when it comes to getting across the jumping puzzle.
Titan Defender
Defender Titan. Pop a bubble and sit in it.
Hunter is probably the hardest.
Titan is a bit easier because they can jump, but I'm tempted to say Warlock just because of self rez. You'd just have to explain how dumb the warlock jump works.
Probably Defender. The jump works as a thruster of sorts which is easy to understand, and a panic Bubble during Conflux will definitely save him from hobgoblin sniper death more than once
Failing that, Sunsinger for melee overahield, self rez when he dies could also work out very well. Just tell him that jumping away from trouble won't work out too well as a floaty Lock![]()
As a day 1 Titan, I approve of all these answers.