It becomes more even if one combine matching infantry units to each attacking artillery. But still any force of defending infantry units only, will dominate any force of heavy artillery (attack on 3) with matching infantry. See the statistics below:

7 Inf

Cost: 21 IPCs

Def: 7*2 = 14

No Units: 7

3 Inf + 3 Art

Cost: 21 IPCs

Att: 3*3 + 3*2 = 15

No Units: 6

**1st Combat Cycle**

Art combo scores: 15/6 = 2,5 hits -> 4,5 inf left

Inf scores: 14/6 = 2,33 hits -> 3 art and 0,67 inf left

**2nd Combat Cycle**

Art combo scores: 3*3/6 + 0,67*2/6 = 1,72 hits -> 2,78 inf left

Inf scores: 4,5*2/6 = 1,5 hits -> 2,17 art left

**3rd Combat Cycle**

Art combo scores: 2,17*3/6 = 1,08 hits -> 1,69 inf left*

Inf scores: 2,782/6 = 0,93 hits -> 1,24 art left

**4th Combat Cycle**

Art combo scores: 1,24*3/6 = 0,62 hits -> 1,07 inf left*

Inf scores: 1,692/6 = 0,56 hits -> 0,68 art left

**5th Combat Cycle**

Art combo scores: 0,68*3/6 = 0,34 hits -> 0,74 inf left*

Inf scores: 1,072/6 = 0,36 hits -> 0,32 art left

**6th Combat Cycle**

Art combo scores: 0,32*3/6 = 0,16 hits -> 0,58 inf left*

Inf scores: 0,742/6 = 0,25 hits -> 0,07 art left

**7th Combat Cycle**

Art combo scores: 0,07*3/6 = 0,04 hits -> 0,54 inf left*

Inf scores: 0,582/6 = 0,19 hits -> no art left