Iron Man and Rescue
vs.
Loki and Valkyrie
Who wins?
Okay. Tough match up. What I think makes the key difference is that Valkyrie has the strength, durability and skill - as well as a weapon - that can seriously damage or kill either Iron Man or rescue. Loki's daggers can hurt Thor, so they're also probably going to penetrate the Iron Man armour.
If it was Iron Man and rescue against Valkyrie by herself, then they'd probably have enough firepower to put her down and 2 on 1 is a tough fight for anyone.
However, the addition of Loki makes it much more interesting- if his magic can fool their sensors then they have a big problem. What Loki would likely do is use an illusion to fake being killed or knocked out and backstab whomever came in close to check.
They've got a massive advantage in terms of mobility and powerful ranged attacks- but if Valkyrie closes with either of them, I doubt their armour would stand up to a dragon fang sword.
As such, terrain is a huge factor - on open ground Valkyrie and Loki are at a big disadvantage. However, Pepper has no real fight training - she just seems to be naturally good at fighting when the story calls for it ( kind of the reverse of plot armour).
All in all, if Loki and Valkyrie actually work together and magic fools team Iron Man's sensors then I give the Asgaridans the win - narrowly, say 6/10 times, with the othe 4/10 they get overwhelmed by Team Iron Man's ranged attacks.