The timer makes you strategize where to use what to be the most efficient posible. It forces you to deal aproprietly with the content. If you removed the timer, it would be extremely easy to reach high levels of mythic +, since the only way to stop you is making the bosses unkillable with your gear.
Mythic + is a system that forces you to eventually fail, restrategize and try again.
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High level mythic + are designed to talk, just not in chat but in voice coms. People communicate a lot more because you need to keep your group informed of what you are going to do.