First of all I'm aware that my suggestions won't be THE solution for everyone, but personally I think that most of the issues would be addressed with it. Also I'd like to make concrete suggestions how to enhance the meta instead of going "too hard, nerf it" or "perfect, keep it that way so I can have it my way", so please keep the comments that way as well.
Now to my suggestions how to enhance the meta so most people would be pleased. Actually in total these are only 3 suggestions overall:
1) Enhance the meta by a strike-like timer
What does that mean? Simple, like in the strikes add a gold / silver / bronze timer, by doing current time = gold, + 10 minutes silver, +10 minutes bronze and else fail, adding a total of 20 minutes of fight in total to the meta.
What would that help? The overall goal can still be beat the current timer, but for random map groups a bronze-meta (with +20 minutes timer) would still be achievable, making the whole meta more accessible to random open world players (one of the biggest complaints in the forums as far as I've seen) and giving loot / more loot for faster players.
I do not know how this could be achieved technically, but since it has already been implemented with strikes it shouldn't be too hard to copy the mechanics?
2) During Exposed-Debuff on boss no tails / side swaps
What does that mean? Quite self-explanatory. During the debuff-phase please disable her skills to use tails or switch sides, thus enhancing the DPS-phase drastically.
What would that help? The DPS-Phase would not be interrupted, thus making more damage on the boss.
Technically that can be achieved with a if not-statement then use skill on debuff.
3) Decrease randomness by setting a max to the skills
What does that mean? Setting a maximum of tails & side-swaps (bites) per x percent would decrease the randomness of getting 7+ tails and 5+ swaps per meta. For example per 20% health a maxium of 2 tail-attacks and 3 swaps makes it somewhat more predictable how the boss run can go (yes, I'm aware that number a total of 10 tails still could be reached, but #2 should fix that as well).
What would that help? Making it for ANet easier to attune the HP of the boss to an expectable average of DPS and making it for players more predictable how often they have to go for tail / swap sides per x% health.
Technically this could be achieved by a counter that resets by x percent health left.
This would be my suggestions how to enhance the jade sea meta and make it more accessible to all groups. Please feel free to comment it.