Well, speaking from the republic POV...
I can get to all of the zones with my un-stealthable character and I only *have* to fight two trash packs which are not mission related.
One pack outside the H4, one pack covering the exit of one of the normal mission entrances.
Stick to edges, jump on ledges and hide from elites.
You can't do the same on the imperial side?
I don't have any problems with it on imp side. Only times i get knocked off bike is if I accidentally agro a jedi special operative (elite in the air strike codes quest area) or a death guard assassin (strong in prison area).