League in-game community is different from League forum community. Downvote me all you want, you know the truth.
Also if you remember Tribunal one game is flagged but the reports from the players that games weigh in. So if X person gets 9 times reports you would see those 9 reports and the notes attached. This would stretch out throughout the player's account and reports/games reported. So Group reporting does affect if it's means is legitimate.
As for making it faster, it won't make it faster but do you look at a burger that has only the patty and buns or a burger that has lettuces, tomatoes, onions, sauces, patties, buns? which looks more appealing? The one with more varieties or in Tribunal case, the more reports one. Which could draw players or the Tribunal reviewers to draw more attention to that account.