It is quite feasible to reach the crit damage cap in a situation where you are getting buffs from other players, like trials. It is also easy to get close enough using CP like Backstabber and Fighting Finesse. It’s even easier on certain classes and on Khajiit.

The ways to add to your crit chance are not as plentiful or as powerful. ZOS has repeatedly lowered crit chance values across the board (set bonuses, CP, and the Thief mundus stone). It generally tends to be more effective to run daggers.

That said, there is a balance point. Your overall damage can be modeled as a function of crit chance and crit damage, which work together. That can also be compared to maces (although pen cap is also rather easy to reach in PvE) and swords (which are often not relatively valuable enough when stacked with all the other weapon/spell damage buffs in a PvE situation to be competitive).

Master's Weapons are almost exclusively used for PVP, where the real benefit is the damage they add to Twin Slashes. Crit has (fairly recently) become a viable source of damage in PVP. Daggers give crit, so they are the popular choice. You can use axes, as they inflict bleed, but bleed damage was "fixed" several times over the last 2 years in PVP so its not as powerful as it once was. Maces are also popular as they give penetration and swords give weapon damage. It really depends on what type of build you are using when it comes to which Master's Weapon will be most effective for you.

Short story long, unless you are running an organized PVP group where you have support roles (healer, tank) providing similar buffs as one would get in a PVE trial, or with others running proc sets that give crit buffs, you are not in danger of hitting a crit cap in Cyrodiil.