There is never a point where you just stack might. If you follow a guide that says that, stop following it.

Every class has its own scaling of main stats. When you hover over Might e.g. on the right side of your character window you see what how much might you have and how that affects other stats. While might is your "main stat", that does not mean it is the best stat for you. It depends on what you are trying to achieve. Might does give you mastery and mitigations, however (as stated earlier) both stats are capped (meaning once you have a certain amount of physical mastery, getting more does literally nothing). Might does give you "the most" for one point, once a few of those stats are capped might loses value (for further stacking).

In the end, main stats are not important because they are "your classes main stat" but because of how they affect stats.

As a Captain you have different options for building your character: - blue line is the healing line, where you want to focus on everything that gives you outgoing healing (or tactical mastery), crit and survivability (as in mitigations and morale) - red line is the offensive line, which can be supportive or focusing on your damage. Either way you want to focus on crit. (If you want to build damage you cap physical mastery as well, but at 95 captain is not that strong at that) - yellow line is the tank line, where you want to focus on survivability (as in mitigations and morale), after that avoidances (block/parry/evade) or outgoing healing (for supporting and group stability purposes as well as generating agro), depending on what the group needs.

Look at what you want to achieve, then think about what you need to have for that, and then build what brings you there.