I think the major issue is the number of players and number of teams per game. If it was a one team vs one team styled PvP game, it would be less frustrating. This goes for both secure and slaughter. If it was 24 v 24, there would be a lot less hesitation with having a team charge in to another team and start a crazy battle. Let the tanks roll in first and pop survival cds while they get focused and stun enemies as your back line starts hitting them and melee start charging in. But this is extremely dangerous in a 24 v 24 v 24 game, why? Because you know the 3rd team is waiting to gank your back line while you are distracted with the other team. This leads into a stalemate or idiots who think they can charge in and do something against a whole team of players (like someone said before).

I honestly don't get how this is more popular than wolves den. I'd say it's probably because people have others to hide behind more often where in wolves den, every class played an important role. I think the issue with FFXIV PvP is, people didn't come to play FFXIV for PvP at all and when it came out, those that tried wolves den were disappointed at not being able to cast as a healer and just getting wrecked, killing the healer population in PvP, making que times insanely high or frustrating most players when they'd que in with a common bad healer that just stood there and did not play right.

I've played against some really REALLY good players in wolves den back before frontlines was out. There were some games that were so much fun because everyone knew how to play in PvP. Neither the enemy healer or my healer dropped immediately and the people you played against and with were people who pvped every day and you knew who they were.

TL : DR - Frontlines brought horrible balance to FFXIV PvP. Wolves Den felt very clunky at first, especially with summoners (before the nerf). But when you were equal geared with your enemies and healers had a decent clue on how to play their role in PvP, it was very well balanced. Wolves Den needs revival.