Are E. Hellfires a good defense against E Megas? If not, then what is the best?
Enforser and eglads are best on base attack. Eglads level 14 makr mincemeat out of emegas.
if you want to use e hellfires for base defense I suggest that you get the hellfire schematic this coming event and put the cryo bomb shell on the hellfires you are using on your base
The drone silo is pretty nice too (some winged drones with shock bombs and some with fire bombs).
Could try the Vanguard as opposed to E.glads, save yr XP for something else.
Putting 4 EShock tanks on 4 sides of your base with 1 ShockTrooper in bunkers will shut down Megas nicely. If you want extra defense, put 1 or 2 EGlads on sides or Enforcer.
EValks in numbers can also crunch Megas nicely.