I have yet to play with IM beyond the destroyer stage, so I can't speak to how its going to play out for heavy ships, but it seems to be a good bonus. The skill is still reducing incoming damage by a pretty decent amount, still has -50% damage to weapons and engines so immediately protects from salamanders, ion chip, and medium hull hits knocking PD offline, and the elite skill protects hull decently.
It lowers the damage of a pulse laser to a hammerhead hull from 100/125 = 80% for no skill to 75/100 = 75% for non elite (not a huge reduction) to 75/150 = 50% for the elite skill, reducing the damage for that mid caliber weapon by 37.5% (quite large). For armor instead of hull, something like a heavy mortar round (110 HE for 220 damage) is going to do 67 damage to 41 damage for a relative reduction of 38.8%, or 38 damage with elite for a relative reduction of 43.3%. All the armor numbers are going to shift around as armor gets depleted, but that doesn't seem too bad, and I feel like a heavy mortar is a decently representative shot for mid caliber guns.
Lets see, for a tempest hull with elite, a pulse laser shot goes from 100/110 = 91% damage to 75/135 = 55.6% damage, or a 38.9% reduction in incoming damage. It goes from 14 shots to kill to 23 shots to kill. Thats a better bonus than damage control gives and is on top of 50% reduced damage to engines and weapons.
Its definitely a lot weaker than it was, but it feels reasonable to me. Without elite it protects armor pretty well (I'd need to do real tests to see how many more shots it allows, but I'd guess half?). With elite it protects hull pretty well - better than the industry skill that actually has a hull damage reduction % for mid caliber shots at least.
So yes the skill is weaker. But it seems to be in a reasonable shape instead of 'multiply hull by 4' levels where all but the largest shot size kinetic guns were reduced to doing minimum damage vs hull.