Again, if there's a generally recognized ideal perk setup it means some perks need revising and until they do, some people will have unfair advantages.
Imagine playing a guy who can use his shotgun at a better range than anybody else in the match. Of course skill is still the biggest factor, but this guy has an advantage I can't gain.
Ultimately I am not familiar with "loot games". I don't care about anything random. I know what I want and like having means to get these things without relying on luck. This is why I love quest exotics and detest random stuff like a Zhalos, which I can't get no matter how hard I try until a chest or raid or NF or Dreg gives it to me.
Lack of re rolls just means everybody will flock to the same vendor weapons instead of the same re rolls. Watch out for 10 billion FWC RLs in PvP once people settle in their loadouts and Mark grind. You already see everybody going for the Vanguard sniper and DO Scout.
I'd much rather be able to roll for what I want than to settle for what vendors sell (what 99% will do) or use my perfect roll only if I'm lucky (what the 1% will use to their advantage).
I see where your coming from. There are positives and negatives to both sides of this argument. It is really exciting to get a vendor weapon you like with better perks randomly though. It feels more special.