Is mechanist weak early on or I'm doing something wrong?

[ReissyBoi]

MCH doesn't really start to get going until level 60 where you unlock 1 of your 3 most potent skills in the form of Drill (58) and potency upgrades to your 1-2 combo. MCH can be one of the strongest jobs for level 60 content just because of Drill, which is a 600 potency skill every 20 secs. It falls off a little bit between 60-75 until you get Air Anchor (76) then Automaton Queen at 80

Also, as Supersnow845 said, item level is a big factor in your damage, more so than your actual level. If your SMN/DNC/RDM are using Shire gear but your MCH is still using Ironworks gear, then it will definitely do much less damage