http://imgur.com/99BsJ4b
My P1 position is always like this. U can also take the counterpart all the way to northwest. This way u have to dodge 1 time (best case) or 2 times (worst case).
P2 I just stay close to egg when it stops moving. Most BLM will take down the cube HP faster than the sphere. Staying close to egg gives u a chance to land thundercloud/firestarter proc on egg whenever u see cube HP is lower than sphere.
P3 most ppl will give BLM special place right behind the boss even when all ppl have to spread for seed, so u can stay at the place all the time, except when u get the nanospore or dodging nerve gas.