I just found a 300HP sub on a 5 star emblem. So... that happened.

When comparing tanks I think it's worth considering how many emblem sub-stat would be needed on one to reach comparable values on another. For example, to bring Vivia's 38 armor up to Matilda's 77 requires the equivalent of two armor sub stats. So, to sate my boredom, let's compare some 3 gear artillery.

M8 -- Mk F3 -- Hedgehog - SubStat

0 -- (-0.82) -- 0 - Critical Multiplier
0 -- (-2.3) -- (-2.3) - Attack Speed
0 -- (0 ) -- (-0.575) - Accuracy
0 -- (+1.93) -- (-5.29) - Damage Value
0 -- (+1 ) -- (+3.15) - Armor
0 -- (+0.2) -- (+8.1) - HP
0 -- (-1.75) -- (-3) - Evasion
0 -- (-1.72) -- (+2) - Rotation
0 -- (+2.65) -- (-2.65) - Move Speed
0 -- (+5 ) -- (-3.3) - Range

0 -- (4.19) -- (-9.04) - Sum

I consider the MK F3 a somewhat tepid upgrade of the M8 benefiting primarily from increased range and blast radius. The Matilda Hedgehog seems a tepid M3 Lee upgrade, a chopped down KV-2, or some meld of the two.