You're right that hots do take time. But the kind of metagame that is encouraged by someone being safe with a full row of hots is bad: it means that if you are facing a resto druid team, you NEED to be able to kill someone in 4 seconds. And burst is already out of hand. Resto druids would (again) become a hard counter to any comp that doesn't thrive on bursting something down in a stun (just like they were in S8). Furthermore the fact that you can pre-hot with no consequence means that in the hands of a good druid your whole team becomes unkillable if hots are enough to keep something alive indefinitely. Again, just flash back to S8 LSD and you'll remember how detrimental that was to the game. If you remember, at that time EVERY tournament team had a resto druid healer, and EVERY team relied on randomly bursting something down in 2 seconds (LSD, When the Stars Align, ATC, etc).
Yes the hot-rolling playstyle might be unique in a game that has largely been homogenized, but it's also detrimental to the metagame.
with the amount of CC in the game right now, just CC him once or twice for let's say 8-12 seconds then add to that 5 globals for hotting up, that's a solid window to "burst" someone down. Generally, damage right now is high enough to do just that. It would require thinking though instead of the mindless meleeing taking place nowadays