I've started playing the game again after quite some time and I've read that Mechanics should affect the Priest seals spells.

I've rerolled my Priest to up his mechanics skill but in the combat log the accuracy of the warding seal remained the same.

Should this be the case?

Thanks

Mechanics don't improve your priest's seals. It's just like that.

Then since they don't get the inherited + accuracy bonus of other spells, they're significantly weaker...

I'll just skip them

They are considered to be hazards and hazards have an inherent acc bonus. So they will hit good enough. Also keep in mind that every spell and ability gets +1 ACC per char level.