I agree with Trindacut that while the "killable" Scarabs are a huge improvement over H2, the player should be able to take them down through repeated massive firepower (as with tank shells to Phantom dropships). This would provide an alternative to the exciting but eventually tiring ritual of boarding them and punching out their energy core. Sometimes, you just want to dodge anti-aircraft fire and let loose with the Hornet's missiles.

Narcogen often refers to Heroic difficulty as the "sweet spot" for Halo campaign gameplay and I tend to agree. It's challenging enough to make Brute chieftain kills satisfying, but not so unforgiving that you can't still run and gun quite a bit.

Having gotten to Cortana level on Heroic (haven't finished the game quite yet), I've noticed two characteristics about Scarabs I think the programmers could have done a lot better:

1. I thought Bungee did a lousy job selecting how much damage the Scarab's energy weapon (i.e., the continuous solid beam, not the overhead turret) does on Heroic. I mean, this is the baddest, meanest weapon the Covies have got. It's supposed to be a walking battle tank of death. It'll chew through the toughest substances on Earth (opening the Control Room in H2's Great Journey level) and take down Pelican dropships with even a glancing hit (opening cutscene to H2's Outskirts level). As a player on Heroic, you should be on edge every time you come up against it. Yet if you PARK your mongoose (or Warthog) within view of a Scarab, even a direct blast from the Scarab's energy beam won't kill you. In fact, half the time, it won't even knock your shields down below 40-50% or kill your marine passenger. Worse, the "punch" of the blast conveniently knocks your vehicle out of its firing stream, and more often than not, you'll land right side up. I understand Bungee's decision to make it relatively easy to avoid the energy blast if you keep moving in a vehicle. But on Heroic difficulty, if it gets you, you should get fried 4 times out of 5. Once I realized it could twiddle my thumbs and eat the first blast from the Scarab, it took most of the glorious tension out of such fights. It honestly felt like it was playing on Normal or even Easy. Compare this with being shot at by Grunt riding a Ghost - you won't last more than 4 seconds unless you take evasive action. Something is wrong there.

2. Did you also find that camping under a Scarab is a bit too safe? In about 50 such battles, I've only been stepped on once or twice. You'd think Bungee could have heightened the excitement by having the big metal beast try to crush you if you hung out underneath too long. If you've ever played Metal Gear Solid 1, you can remember just how long you'd last if you tried to walk underneath Metal Gear during one of the last boss battles.