No.
The leaver penalty does not need to be increased, especially not when you stop to consider that not everyone who leaves does so intentionally.
It’s already unfair to penalise players who get disconnected due to circumstances beyond their control (eg power blackouts, unscheduled internet service interruptions, hardware failures, etc).
Making said penalty more severe is not the answer.
Backfill for Competitive is the only viable solution for the leaver problem, and it would also help reduce queue times because the game wouldn’t be sending 11 players back to the queue if someone disconnects in the first minute.