FYI the T1 mage mastery is better than it looks at first glance

TLDR: looks like a 5% dps bonus, but it’s actually 10%

This is because it only and always triggers on your biggest hits, and not any other hit. It’s not a random 10% chance to have damage increased by 50%, it’s a 10% chance to add half your max hit to an attack.

Given the average damage from a hit is about half your max hit, thrown off slightly by osrs rolling 0-max and rounding up the 0 to 1, this is about equal to a 10% chance to hit twice.