The effectiveness of teleport in emergency situations has not been blunted--if you don't have much PP, you can always HPCast.
No fighter in their right mind would contemplate HP casting unless the only alternative was death since it now abuses Wi and To. The effectiveness
has been blunted. I just experienced it first hand! Instead of being able to teleport twice, I was able to only teleport once (but it failed). It literally just happened to me the other day. I didn't die, but it handicapped me significantly. I had to stick around a cavernous level and fight a Master Lich who spawned a bunch of stat draining undead while contending with jellies, a mimic, and a cat. If I had a second teleport, things would have been made a lot simpler.
That's not to say that there couldn't have been other ways to get out of the situation. I managed to make the best of the situation (PoEx, AoFA, Wand of Fireballs, Arrows of Undead Slaying, etc.) The point is that this change took away my best option, i.e., it significantly handicapped my PC. The problem with only being able to teleport once is that it's not infrequent for you to fail because some monster is standing on the square. The ability to teleport twice in succession versus the ability to cast teleport only once is a very big difference.
Being able to teleport instead of walk is convenient for wizards and helps them avoid some corruption. However, letting them only do this half as much is a minor inconvenience. They're still going to do it. It's a minor nerf at best. The wizards I played were rarely using up any significant portion of their mana teleporting anyway. This change affects melee PCs who have some small proficiency in magic far, far harder than it does casters. As usual, melee gets the short end of the stick.
This change didn't nerf non-casters AT ALL; I have no idea what you're talking about.
My mist elf duelist got hundreds of castings of teleport after eating the oracle, drinking some PoGA, wearing +Le gear, and drinking a potion of boost learning while reading from a blessed Spellbook of Teleport. Unfortunately even with a Mana stat of 25+ he could only manage to cast teleport once. I felt pretty intensely nerfed, which is why I made this post.
books are rare enough that they're somewhat unlikely to find one
If I recall correctly there's a guaranteed Spellbook of Teleport from Khelly. That's where I usually get mine.