Since only top500 of Immortal players are radiant rank there is a massive skill difference between the bottom immortals and the top immortals close to radiant, However they are all still displayed by the same badge and rank which is supposed to determine and present their skill level.

I would suggest that while keeping Radiant top500 that you split immortal into 3 tiers again while keeping the leaderboards:

Radiant - Top 500

Immortal 3 - Top 1500

Immortal 2 - Top 5000

Immortal 1 - Rest of the immortals.

This would create more of a purpose for the immortals to grind since for them it might seem impossible to reach radiant however they still want to present a higher skill level than the other immortals.

I also just hate the fact that all immortals have the imm1 badge in game, career and dorito considering it was said to be imm3 :/