The DC guidelines say examples of DC16 actions are "Pick a typical lock" and "Cross a wildly swaying rope bridge".So Rogues automatically succeed at Hard Tasks they are skilled in, right?
Skill Mastery (10) + Skill Mastery or Ability (+3 or more) + Skill (+3) = 16+
Is this correct?
How do you feel about it?
Would setting a Hard DC to 17 be better?
I see no good reason why rogues should be better at using their skills than anyone else is. They already get far more skills than anyone else, thanks to getting two backgrounds. Why should a Rogue Sage be better at Lore skills than a Wizard Sage? Ditto for any other class/background combination.
Because the rogue is the skill expert (one of them) and the wizard is a magic expert (one of them).
You're just stating how it is as justification for it being that way. Why should the rogue be the "skill expert?" Skills are something everyone has. Why should rogues be better at it than anyone else? They have many other niches they can fill that are far less boring and controversial.
It would be cool, for example, if they let rogues trade sneak attack damage for special attacks the same way fighters can give up combat superiority dice. Things like inflicting Bleed damage, blinding foes, disrupting spellcasting and other dirty tricks are things I'd like to see them be able to do. I'd also like to see them get choices of other cool special abilities, like evasion, hide in plain sight, disguise, forgery, and use magic device, to name a few. Those things are, IMO, alot cooler and more distinctive than "I can take 10 on any skill!"
And it shoots up to 11 already by level 5

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.