[0.915] I finished Insane Difficulty with 10 Insane AIs via Master Quest Victory on Season 151.
I would agree that Path of the Assassin is the best Path when you are outnumbered. Even if only a bit of damage normally slips through to the enemy, if you have a high crit chance and damage you can punch through even the heaviest armor. Plus all the buffs with Procipinee's Crown including Regeneration of 3 or 4 per turn, and even when you do get damaged you heal it up. The most essential part of the armor, apart from heavy enough armor - the Ivory Helm. Being able to crit and being immune to crits is an awesome combination! I would say that the Ivory Helm is the best helm there is, because being able to avoid all crits (which can get quite big and knock you out quickly!) is one of the best specials.
I didn't end up using any army units, but I did lots of quests via the Quest creator item worth 100 gold. I only lost one quest, the Garrote quest against the slags, and I eventually took them down a long time later. I also used the Broken Loyalties spell to capture Karavox's city. =)
Here is my Sov start and the victory screen:


