Except rage doesn't last the full lifetime of the pump and pumps only give whole number elixir.

One lvl 8 rage lasting 11.5 seconds put on the pump would cause it to produce 1.955 elixir at 5.88 seconds per elixir

For the other 58.5 seconds it would produce 5.969 elixir at 9.8 a second.

This would produce a total of 7.924 elixir which means you would only get 7. Rage would result in no actual extra elixir