Combat Jump.
I'd probably go CJ just cause its anti imob is so damned helpful to be thrown in. My blaster has it (not for defence) and I find it useful by itself. Taking hover I'd want to slot for both defence and fly speed so a conflict of interest.
CJ and Manoeuvres combined might work out to a minimal defence level and give nice places for IOs
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
Either another attack, or dropping something and getting aid self 
CJ, hover etc. aren't going to make any real difference in terms of survivability unless you've got other def to stack them with.
Took CJ, and found an odd side benefit - having CJ active improves flyspeed by about 20% 
...and yes, it's mostly for the IO benefits... already got the +Acc bonus, but not liable to get the +Recharge one unless I've got 35 mill to spare...
Is it time for the dance of joy yet?
Having 6 slotted on my defender I can confirm its a lot of expense trying to get all the small benefits. I dont have many characters without CJ though, and the defender is the only one that gained it for IO slotting. Its one of my favourite movement powers in the game simply for control. It stops the drift of fly for a start
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
In which case, CJ would go nicely with Frozen Armour from Cold Mastery. Stealth, Hover, Combat Jumping all together would you give you +7% Defense to everything. Which in my opinion, is pretty damn good. And if you take weave aswell, that's 10.5% defense to all damage types.
Here's the full list.
Stealth: +3.5% Defense to all damage types.
Combat Jumping: +1.75% defense to all damage types.
Hover: +1.75% defense to all damage types.
Weave: +3.55% defense to all damage types.
Invisiblity: +7% defense to all damage types.
Frozen Armour: +10.5% defense to S/l.
Maneuvers: +2.28% defense to all damage types.
Hope this helps. 
-Petitioned.
But Stealth And invis have their defence halved when you attack/are attacked.
But of course, attacking from stealth is always a good "Defence", in the sense that you control the start of the fight.
stealth is a great defence as your aggro range is reduced to begin with. I run with stealth and combat jumping personally, acrobatics just makes m life that much easier although saying that, there is no better melee defence than hovering out of arms reach 
I wouldnt give a monkeys about any type of defence other than 'active defence' ie stuns and controls, these far outweigh the likely def a blaster gets, anyway either take cj for the resist to immobs or stealth for -per or hover to aerial kite efficiently.
Combat jump should be doing this to a blaster:
200% JumpHeight to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Melee_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Ranged_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(AOE_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Smashing_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Lethal_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Fire_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Cold_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Energy_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Negative_Energy_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1.75% Defence(Psionic_Attack) to Self for 0.75 seconds
Effect does not stack from same caster
1% SpeedJumping to Self for 0.75 seconds
Effect does not stack from same caster
4000% MovementControl to Self for 0.75 seconds
Effect does not stack from same caster
20% MovementFriction to Self for 0.75 seconds<--flight speed improves of this maybe?
Effect does not stack from same caster
-8.304 Immobilize to Self for 0.75 seconds
Effect does not stack from same caster
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
I don't think it improves flight speed. It just removes the inertia associated with flight so I guess reduces total flight time if you turn a lot. Inertial Reduction from Kins is the same. Still nice for zooming through missions without getting yourself stuck on pipes and desks and such!
Yeah better aerial control
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
[ QUOTE ]
I don't think it improves flight speed. It just removes the inertia associated with flight so I guess reduces total flight time if you turn a lot.
[/ QUOTE ]
Inertial thing is true and handy, but I tested it on straight-line flight in Steel and boosts your flight speed by roughly 10%. Add on Sprint and the Jump pack and I can crank about a 25% boost, then use Power Boost and it's about 40% faster than normal in short bursts. When Paragon's in danger, you need all the help you can get
Is it time for the dance of joy yet?
...isn't always a good offence.
Assuming I've got just one spare power slot, what would be the best +DEF deal out of:
Hover
Combat Jump
Stealth
Other (insert name here)
PS:Fly is my main power set - just because I like it and I like to type when travelling to missions. And I ain't changing.
Is it time for the dance of joy yet?