If you absolutely must have randomness and can't appreciate the standard rules for their simplicity and speed,
The problem with the "simple rules" in the PHB are that they have holes big enough to drive a truck through. It has nothing to do with the randomness factor.
"The DM compares the Stealth checks of anyone hiding with the passive perception score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter."
First off, the word "hiding". Stealth is not just used for hiding, so PCs or NPCs not hiding cannot surprise anyone (according to this rule). PCs or NPCs just sneaking down a corridor, for example, cannot surprise anyone. Let's assume for a moment that this is just bad writing and that we can replace the word "hiding" with the phrase "using that skill" and move on.
Let's take the example of 5 monsters hiding in the room vs. 5 PCs sneaking down a corridor.
The DM has to roll 5 stealth checks for the monsters. Each player has to roll a stealth check for his PC.
Almost always, at least one of the monsters will roll so low that all of the PCs will notice him. Almost always, at least one of the PCs will roll so low that all of the monsters will notice him.
Almost always, there will be no surprise.
What good is having the rules if following them means that those dice rolls will be in vain the majority of the time and almost never work. Surprise will almost never occur. In this example, 10 dice are rolled and the results of those rolls is that nobody is surprised 95+% of the time. Talk about wasting time rolling dice.
This is why both sides have to roll group stealth checks. That way, typically some PCs will notice and some will not and be surprised. Typically, some monsters will notice and some will not and be surprised.
Unfortunately, the PHB does not mention group stealth checks at all. Many DMs who do not read message boards will never figure it out and will probably use some set of house rules anyway.