Well you can see the test at shark (2 def) an green slime (0 def). The ichor only add 1 damage to shark, and no effect on green slime.
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For Sniper Rifle, as the damage is actually from 85% to 115% of the original damage (so, the if the damage is 200, which is similar to the sniper rifle's, it could be from 170 to 230) and the test may not be accurate due to RNG issues.
And the wiki may not always be right, for example, the expert enemies' defence is NOT more effective and just the same as normal mode.
Finally, the Ale is not a simply 20% damage, it increases 10% damage, 2% crit chance and 10% melee speed, and the 10% melee speed is actually quite complicate, it varies from no effect at all to a 50% increased DPS, depending on the weapon, the weapon's modifier and other melee speed increasing, see
here for details.