The lowest possible combat would be just around 80. However, the lowest EFFECTIVE combat level would be slightly under 100. At 80 combat storm of armadyl has no point vs pures. At 100 combat you can surprise loads of people.
I suggest you to make this
60 attack
90 strength
70 defence
99 ranged
77 prayer
99 magic
95 hitpoints
92 summoning
combat 99+12
Wolpertinger, piety, rigour, augury. Just tribrid with Storm of armadyl + chaotic c'bow + claws + stream necklace. I've seen one guy doing it with nearly the same stats above, except that he had 99 hitpoints and 88 strength.