The knockback is ineffective because force leaps/charges, and obliterates can be used while the opponent is still in mid-air. They don't even have to land. In less than a second they've back on you, and you've recharged their shockwave so they can crit-smash you again.
Shield only lessens *ranged* damage. It does not mitigate melee attacks. Cleanse does not get rid of force-based effects, so only fire-effects and poison-effects used by other Troopers/Bounty Hunters and Agents/Smugglers are mitigated. It won't remove any melee snare.
The only abilities that can be used while on the move are things like explosive dart, rapid shots, and the missile blast. That's it. Three attacks. Using the root punch is also not effective because the amount of time they're rooted: 1) You are always in melee range, so you eat a ravage/master strike, and 2) By the time you move out of melee range, you won't have the time to get off any casted moves.