It's still early, changes can and will come. Keep in mind these changes usually have the end of the current xpac in mind as well, and some reflect those. As to your points:
1: they are probably starting the AoE off based on current tier. Like my point, current AoE is capped for tier. Changes possibly reflect this.
2: same issue MM had at the beginning of Legion with Vulnerable. Changes made close to mid xpac to adjust damage values.
3: cast time might be long, but if it's a "holy shit what just ran you over" damage ability, or affects other abilities, 3 second cast might be necessary. Haste values will also bring this down, and might make haste a #1 secondary stat.
4: MM has always been squishy compared to the other 2 specs.
SV is meant to have mobility with Harpoon resets. Blizz is just incrqseing it somewhat with giving Disengage baseline and the option for posthaste.
SV currently has quite a bit of healing thru RS, Exhiliration kill reduction, Turtle.
Pet baseline is required for abilities, as KC is now a focus builder. MM also hasn't taken a pet for 3 xpacs for anything other than solo content where it is required.
I'd rather have consistent damage on SV next xpac than what we have now: ramp up time and complete loss of damage if off the boss or add for any decent amount time.