I believe he was talking about two different events.
They were in close enough proximity for me to link them, but hopefully he was.
Giving up class levels in a full caster class is usually a negative. Gaining fire resistance at low levels is no match for gaining miracle at higher levels, which is ultimately what the character is giving up. I would have said Hussar was nerfing his character in favor of flavor.
Again, it depends on the game. Will this game reach L17+? Do frequent opponents have fire attacks?
I think the important part to remember is that it's really not combat potency or skills that need balance, those are indeed a matter of character and campaign choices, but rather the narrative control elements that are primarily limited to casters. It's the utility of these classes that make balance an issue. Take for instance one of the most power narrative spells out there, teleport. This simple spell (or that variations that clerics and druids get), allows the character to bypass the narrative the DM has laid out in the game. You must travel the misty road to the tower of blah blah and do this important thing. The fighter shrugs and heads toward the road, it's his only option. The Wizard smirks and says haha to your narrative, I'm going to bypass all that and appear at the tower instead. Even spells like Speak with Dead, Rope Trick, Fly, Scrying, etc have profound effects on the narrative of the game. Now a practiced DM will have taken into account these elements, having played with them for possibly decades, but a inexperienced DM will be a bit flummoxed by them, as we all probably were the first time a group of players said, nah, we're going to bypass everything you created for tonight's game and jump right to the city across the sea.
If we read the spells in the manner that most suits the PC's, I suppose. How far away is that tower? Teleport allows 100 miles per level. How big is the team? One additional creature per 3 caster levels - horses and other Large creatures count double. Leaving the mounts and animal companions behind? "You must have some clear idea of the location and layout of the destination. The clearer your mental image, the more likely the teleportation works." So, how clear is your mental image of that tower (or should I say the courtyard in the tower)? "Areas of strong physical or magical energy may make teleportation more hazardous or even impossible. " GM prerogative to make Teleport useless.
Greater Teleport? Sure - that's a L7 spell slot. Still limited in the number of passengers. And "You must have some clear idea of the location and layout of the destination or a reliable description of the place to which you are teleporting. If you attempt to teleport with insufficient information (or with misleading information), you disappear and simply reappear in your original location." Not seeing this as the universal solution it is commonly presented as.
One balancing factor is scenarios that don't allow the spellcasters free reign to blow off their entire repertoire, then plop to the ground and sleep as the mood strikes them. Rope Trick is far from unbeatable. And let's remember those extradimensional space rules - where's that Bag of Holding with your spellbook in it again?