Striker
Inflict strong stun when boost is broken.
Both recon and guardian shields take longer to fully recharge when broken, striker shields recharge instantly after 3 seconds regardless if broken or barely used. Since strikers rely a lot on their shield, there should be a bigger penalty to overusing it. When the boost breaks, it creates a minor, non-damaging, blast that stuns the user. After 5 seconds, it instantly recovers.
Recon
Allow recon deathmark to break shields.
In the rock, paper, scissors of Lockdown, recons are supposed to beat strikers. In reality, they get shredded 90% of the time. Instead, give recons shield breaking abilities so they can beat guardians. Guardians are slower and make better targets for the slow recon.
Guardian
Make guardian shield flinch-proof
Guardians are built to check strikers. They have much more health and can stall out boost with their tanking ability. The main reason strikers can beat guardians is because they can stun lock and break down the shield without having to run away that much. Making guardian shield flinch-proof will allow guardians to lash back at strikers more easily.
Walk speed is still going to be a problem with these classes. A smart striker will just boost out of gun range while he/she waits for shield to regen with no penalties other than missing out on damage. Making strikers only fast when boosting and slower than other classes when not boosting will let other classes be able to attack them with swords more easily (the real damaging weapon class in LD).
Recon Footsteps shouldn't exist as it gives away their position and with deathmark constantly telling your enemies when you are near it gets hard to sneak up on people.
Guardians used to be OK but with so many sets capable of dealing high damage their shields can't tank as well as they used to.... what is the point of being flinch immune when your enemy can just kite about you with a gun?