The power output also matches the level of the skill, so if you learned a new sword skill and it's level 1, it would probably be under powered compared to the skills you have had time to master.
The only thing that is necessary to destroy the golem, is that the impact from the landing travel inside the golem and shatter it's core, you don't really need to damage anything else.
The only useful melee secondary i have ever seen is either a buckler that can be use offensively or a parrying knife. Historically dual wielding have only really been used during flashy duels that’s been put up for entertainment purposes.