I was pretty downright thrilled with those fights. The acoustics of all three times a lightsaber encountered Mandalorian iron were just incredible.
My understanding is that the pure form was believed to be lightsaber resistant, along with cortosis (which actually shorts out blades), and phrik, a third somehow lightsaber resistant material. Although my sources are rusty at the momentand I have a good chunk of the clone trooper novels to still get through properly.
I am also intrigued how in one fight a certain character does intentionally lock with the spear briefly and it does begin to glow red... Perhaps hinting at familiarity of fighting mandalorians with that particular saber, and trying to get the metal to a melting point by sustained contact? Obviously there is some melting point for the forage to work but it's interesting to wonder if lightsabers can eventually cut their way through but only with great difficulty and time.
Well in attempts to not spoil the show - Moff Gideon (lore wise) both has experience fighting Mandalorians, and with the Dark Saber. He took it off Mandoes after all.
And I *believe* there are theories that the Dark Saber is different than other light sabers. Again, read through other posters in other forums - not really looked into myself.
But yes, I too appreciated that at least with that 'thin' spear - it was heating up with 'extended' battle contact. Thereby implying that if con't long enough it could/would start to 'bend.'
Just sad we had to wait 2 seasons to get Pedro Pascal both a spear, and a spear-fight scene. Considering that's his 'thing' (a technique he got skeels with before, or For, his role in GoT), I was hoping to see a lot more such action before the pinnacle of Season 2!
But yea, "light saber resistant" has certainly been Disney cannoned as "Light saber PROOF" - no one gets through Din's armor, with *anything*, for the 2 seasons so far.