Way too overpowered.
How many points?
Also, the stats are even better than an Avatar. A god of war. And then you've got the 2+ re-rollable, the 3+ inv save that is immune to the effects of weapons that ignore inv saves, no less that 3+ to wound, he only needs a 3+ to wound you, no matter what your toughness is and it ignores inv + Armour saves, gets his squad (Including him I take it) to T10, so that's five WS10 S10 hits. He also has 2 different CC weapons, so how many attacks does he get from each 1? 4 from the hammer and 1 from the fist? 2 from the hammer, 3 from the fist? and so on.
It goes on.
Horus would have to be incredibly expensive 500-750pts. Maybe revise some of those rules.