easl: to clarify, in our WFRP, all players have the same role, which is "trooper" in the Imperial Army. In most cases, they will advance just a little...

Novice mage is worth as much as a rat catcher. I agree with most of the arguments from "WHFR 4e - Are Wizards playable?". After some "level" they get powerfull, but our PCs never get there.
So far we played only humans, as you can't play elves in WFRP 1ed. I'm evaluating if migration to WFRP 4th will solve this and we could add other races. So far, I think it's not possible.
Orin J. You pinpoint issue which I'm afraid: "if hi concern is that he thinks one of his players will try an elf and start overshadowing the other players and make them unhappy"
This is exactly what I see, as an outcome of rules and high elves stats. We enjoy competing between players. We count how many "headshots" each player have. We enjoy successes of heroic actions and count them as well. So-called "roleplay" based on the fact that "elves" should be the best to sneak through the forest is not our type. I don't understand why this is "Bad" RPG and a "party problem" to solve as it's fun for all of us what we do.
Regarding: "If the NPCs see a party with a merchant, mystic, and elf knight, Why wouldn't they assess the knight as the biggest threat and throw every trick at him?"
This is exactly what we do - all encounters have a lot of tactics and we (GM and team) use all possible advantages (terrain, surprise, etc.). So far I've tested that mixed specialties don't work. Is it only me? In WFRP 4th, so far all weaklings (low-level mages, exposed rangers etc. btw. anyone who has 20% lower WS below average - yes so far this looks that bad!), get annihilated instantly. Close combat with a bow doesn't work in 4th and I like this. Am I wrong? But this means that if the ranger will lose protection, he is considered dead.
I'm still learning in WFRP 4th, so for example, I didn't go through all the skills yet. I wasn't aware of Beat Blade, but it looks like it's only available for Duelist. "Beneath Notice" it's limited to only a few career paths, so it's not very often that NPC will get those. I'll add those, but I doubt if all enemies should have it...
"Distract" - I have no idea how you would like to use it, as it needs "move" action.
Anyway - thanks for all input, I'm learning and I will reevaluate and tests your suggestions.