Springing into and out of a flanking position also leaves your partner out to dry. He won't even get the flanking bonus and will receive all the attacks. Also, if a Monk is using spring attack, he isn't using Flurry of Blows and his improved unarmed attack rate.
Also, Monks have greater stat depency than fighters. A fighter wants big strength and Con, and some 13s for feat access. A monk wants high everything except Charisma. I usually give PCs a generous 35 point buy. You can usually get 2 good stats and some decent scores, or get a bunch of moderately good stats. A fighter can go 18/16, 16/18, or 16/16 and still have acceptable other stats. On the other hand, a monk can use almost all stats. He fights, so he needs HP. He doesn't wear armor, so he needs Dex and Wis. WIS also helps many of his special abilities. Strength adds damage. Monks also have a skill list that asks for more than 4 skills, so a decent INT is useful too, but not completely necessary. If the monk goes Dex and Wis, he's well defended, but his damage sucks and he needs to spend a feat on weapon finess. On the other hand, without Dex and Wis as his good stats, his AC won't be so great. Without a godlike set of rolls, the monk is going to suffer somewhere.
Quivering Palm only works against creatures with less HD than the monk. You said something about big red dragons, with 30+ HD.

In any case, similar instant death effects on a failed save exist. Even the lowly 1st level command can grant a coup de grace - almost instant death - on a failed save in certain conditions. Slay Living can be cast 6 levels earlier than a monk gets Quivering Palm, and is better.
BTW, Spell Resistance is in the general cleric list too. But a wizard has a 55% chance against an equal level Monk's SR, and might have Spell Penetration or other effects. And it's not as if every spell the wizard has needs to be aimed at the monk. Defensive spells, buffs on the wizard's allies - the guy fighting the monk perhaps - or attacks on the monk's friends still work. Summoning stuff can work too.