Why does Medusa have low pick and win rate? She seems extremely strong/ can take a lot of damage

Medusa has ~47% win rate and ~2.4% pick rate, while she can take much more damage than other heroes. Wouldn't that make her a strong offlaner?

Why I think Medusa is strong:

If you consider her mana bar her hp bar, she reduces damage by 72% (1 – 1/3.6; provided Medusa has mana). In perspective: Bristleback reduces damage by 40% (from the back).

Side notes: Medusa mana shield can not be broken with Silver Edge, but does not return damage when attacked like BB, Spectre.

​

(numbers below are @ level 30 with no items from full hp to death)

Number of dagon 5 hits from CM level 30

Number of rapier hits from CM level 30

Number of rapier + deso hits from CM level 30

Time to death from Necrophos passive (level 30, 2 HoTs and Aghs)

​

Medusa's mechanics seem extremely strong vs. some heroes/strategies while being extremely weak vs. others (not exhaustive).

Strong

• vs. Necrophos: Medusa has low max. hp and is mostly (close to) full hp, so Necrophos' passive and ult are not as effective as against other (tanky) heroes
• vs. pure damage: most heroes cannot reduce pure damage, some exceptions are Spectre, Bristleback. Some item solutions: more raw HP, blademail, evasion, BKB. Medusa has the best reducing capability taking only 2% of the pure damage with HP + 28% of the damage with mana (1/3.6)
• vs. damage amp strategies: Medusa's mana pool takes the raw damage amount, so it is not amplified by e.g. minus armor (deso, solar crest, Slardar, TA, Weaver, etc.). Only the 2% damage affecting HP is amplified. Conversely, reducing damage (e.g. Pipe, armor) is not effective on Medusa until you have no mana left.

Weak

• vs. mana burn/steal
• vs. Axe: Axe can dunk Medusa from full hp (if she has no hp items)

​

Itemization

I am not set on the items yet. Some thoughts:

Good

• Blademail/radiance: usually good on tanky heroes, damage reflection works the same on medusa as other heroes. (Radiance disassemble into rapier + butterfly)
• Bloodstone: activate for large mana regen from spell damage
• Octarine; lot of mana and mana regen and more uptime on snake and ult
• Hex: lot of mana and mana regen, strong disable
• Butterfly: attack speed, attack damage, evasion; good offensive and defensive
• Mjolnir active: reflect damage when being attacked. mana regen in combination with Bloodstone
• Phylactery: mana, hp, slow, mana regen. CD almost the same as snake (6s vs. 7s)
• Mask of madness: active negative armor doesn't affect medusa as much as others

Bad

• Damage reduction: armor, pipe, etc. is not effective
• Attack modifiers before level 25 talent (split shot uses modifiers)
• Eternal shroud: mana regen component only works when you have no mana anymore

Of course, being able to take damage is only one part. Nevertheless Medusa seems good at it.