I was wondering if all HM difficulties are similar. What I mean is, can a fresh 50 do BT with the same amount of difficulty if they were to do Foundry or do they have to work their way up?

The HM's scale up in difficulty similar to how the normal modes scaled up in difficulty as you levelled up and did them.

 

Geared 50's will clear BT incredibly quickly without even trying. Similarly true with boarding party and foundry. Fresh 50's will likely find HM BT a comparable challenge to when they first did BT at low levels. They will however likely have more trouble with BP and Foundry.

 

HM directive 7 is a pain just because of bulwark's short enrage timer. This places the main stress on your DPS being sufficiently geared and good enough at their class to take him out before he rages.

 

The ilum and Kaon hard modes are a higher level of difficulty, though with a competent geared group, still quite easy except for one or two specific bosses.