The JIRA currently has well over 2,000 open issues listed.
This has multiple effects:
Because items are hard to find many duplicates are posted. An item with 20 votes is just as important as an item with 20 duplicates, but the later is harder to identify.
Developers are presumably wary of using the JIRA to find problems to resolve because of the sheer volume.
New users are wary of using the JIRA because of it's sheer scale.
Voting is ineffective while votes are cast across many related / duplicate issues and those votes are not transferred to issues once a duplicate is identified and linked.
Rather than suggest a new voting system or some reform of the JIRA that only it's creators can code. Assign more resources to maintaining the existing JIRA. If one person spent all day, every day identifying duplicates, closing non or out dated issues, creating and adding to meta issues and so on, the JIRA could be considerably compressed and be of much more use to both users and developers. That person would also be very well placed to suggest new categories or other improvements within the existing framework. The same person would also be an excellent point of contact within LL when trying to identify the current main issues.
This is something that in theory any user can do, but clearly in practise it isn't happening enough or with consistency. It's going to take some kind of paid allotted time to sift through and it seems wiser to have someone on the Linden side doing the linking and closing of related issues.
Note: Please link related issues rather than just close them without linking. It's important to see that 20 people opened the same kind of entry and adds weight when prioritising the main issues.