GM player here
-Assassin is in a bad state where literally only Qiyana and Kha'zix are the only above average/great assassins. Nocturne got nerfed to the ground due to blender nerfs, Diana is for early game, LeBlanc is for woodland comps and don't shine in assassin comps, Zed is too expensive and requires items that can't really be used on anyone else mid game to even function as a decent unit. 3 Assassin Buff is only minor, just gives them some help. 6 Assassins will not be good, as you are still holding a lot of units not worth keeping for the entire duration of the game.
-Inferno needs a bit of a buff. Not that good at 3, and 6 is really risky due to the ocean nerfs and the lack of front line. Needs an inferno spat to function correctly, and you are giving up a rod for that which is probably the best item in the game for carries.
-Mages are not the strongest comp in the game. The Sivir and Friends comp is the strongest currently. The only good mage is Brand, and even then Brand is a really expensive unit to chase. He is also clunky in that his ult still manages to fizzle out sometimes, and he only shines in 3 mage comps. Even then, 3 mage comps is whatever because you are keeping in 2 crappy units for a chance of double casting. 6 mage buff is needed, the comp is just bad.
-You only run lunar as a side benefit for how good the two lunar units are. No one cares about the lunar buff, and are fine transitioning it out when there is a chance. The units themselves are broken and got nerfed because of it.