Except that it really isn't the equivalent - the majority of the damage potential, the primary attack, would be affected by the range 3 defence bonus, and having two attacks to make in a round prevents the Defender from modifying them as easily as a single HLC shot, as well as all but guaranteeing Rex's ability, already a 'when the planets align' event, comes into play even less.
When even a modestly upgraded Defender can easily surpass 40pts, a saving of 4-5 points but a drastic reduction in damage compared to the HLC option doesn't help - when you're spending those kinds of points on a single, fairly fragile ship, it needs to be throwing out a LOT of damage to compensate.
Personally, I think the long-overdue Defender fix could be as simple as a discount of 3/4 points on all cannons, or as complex as my personal ideas:
'Onyx Squadron Elite'
Title - TIE Defender Only
If your Pilot Skill is "5" or lower, increase your Pilot Skill by 2, and your upgrade bar gains one EPT icon.
After executing a green manoeuvre, you may recover 1 shield.
Linked Cannon System
Cannon - TIE Defender Only. Limited.
Your upgrade bar gains one Cannon icon.
After performing a primary weapon attack, if the attack hits, you may apply any non-damage effects from an equipped Cannon upgrade card without cancelling attack dice.
'Fluff' for the Defender is the main inspiration for these abilities (a dangerous precedent, perhaps):
-Allegedly the best pilots in the Imperial fleet, it seems thematically flawed that their generic PS values are lower when compared with the generics for every other ship besides the TIE Fighter and Interceptor. At the same time, I don't think a base PS10 would be reasonable, hence the restriction of this part of the card to the generic pilots. The addition of the EPT to the generics would help make them a lot more viable, also.
-Repeatedly the Defender is described as being fast, while also having rapidly regenerating shields that did not overly tax propulsion. The second ability of the title follows this description, and addresses the Defenders comparative frailty in combat. Restricting this to green manoeuvres keeps shield regeneration in line with R2-D2 while also allowing the Defender to maintain speed, given that its 5-straight is natively green.
-The linked cannon is listed as a standard configuration, so to my mind it makes sense to allow it to be equipped without 'using up' existing slots, and without spending many additional points over the cost of the cannon itself. It makes Flechette or Ion cannons a viable selection for Defenders, without affecting the Heavy Laser or Mangler choices, while also allowing them to do something unique - i.e. allowing them to do full damage with the 'control' cannons.
Personally, I don't think adding Boost helps the Defender where it is most lacking, and I don't think it should have access to Autothrusters - it's not a very creative solution to the problem and would prevent the MKII Engine being used.
What if the shield regen was on RED maneuvers? Since defenders have a lot of them, and it provides a trade off, and it gives a slightly different mechanic from r2.