This is a personal observation, but Rage is what makes Super Strength feel like it is Super Strength. If you "cottage rule" it into something else, it will feel like the set is missing something.
It's one of the reasons why I don't particularly care for Dark Melee on Stalkers. Yes they all need to have Build Up as part of their kit, but to me I just don't feel like the set is complete. On my Scrapper practically have perma on Soul Drain (3 second gap), so the uptime with with Rage doesn't really make it unique. Soul Drain doesn't have any crash of any sort, but the low end is also lower than a regular Build Up with just 1 target. However, it does also make up for a higher cap, at 150% Damage and 30% ToHit when you're max mob farming.