I just happened to wander into this thread. Sorry for not posting earlier.
My pet survives in many of the high end encounters partially because of the AAs I have obtained. Partially because of the skills of the groups I am included within. On mobs with high rampage DPS pet management is one of the key items I use to keep the pet alive. I am usually in the DPS group that often has a paladin healing with their group heal spells. Pet Affinity allows my pet to benefit from those spells. Mobs that output more damage than those heals can help are much more difficult for him to survive. I find myself monitoring his health during those fights and may use my pet mend, or even step out of combat to cast my own quick heal to supplement the group heals. One of the other things I try to keep a close eye on is the directionality of the fight. I work hard trying to ensure the pet is behind the mobs. DonĂƒÆ’Ă‚¢ĂƒÂ¢Ă¢â‚¬Å¡Ă‚¬ĂƒÂ¢Ă¢â‚¬Å¾Ă‚¢t confuse enrage damage with the rampage damage. If the pet starts eating enrage damage he is dead, no way I can keep him alive through it.

If the pet is getting beaten up too bad during the fight I will pull him off the mob and wait for some heals to hit him before I send him back in to combat. /pet hold is a critical part of that working. However, I do feel your pain, keeping a pet alive on raid level encounters is difficult. I do not feel that my pet has all that much more power or survivability over the mage pets, in fact he may have less HPs than the level 70 earth pet. (I have a lev 70 mage as well.)
I will do some testing comparing the 2 pets this week to see how they differ. I do know that my mage can do pretty good DPS even if his pet dies during a raid encounter. The bst pet does take quite the hit from rampage damage, and on some mobs it is inevitable that he is going to die in combat. One of the warders in ST will pretty much kill him immediately due to rampage, the rampage damage is more than can be healed based on his hps. I forget which one is it off the top of my head. Dagarn in NToV is another that eats the pet pretty fast if I am not watching him very closely. There are a few others that just do so much AE damage that pets simply donĂƒÆ’Ă‚¢ĂƒÂ¢Ă¢â‚¬Å¡Ă‚¬ĂƒÂ¢Ă¢â‚¬Å¾Ă‚¢t have the HPs to survive. However, the same could be said about me. ĂƒÆ’Ă‚¯Ăƒâ€šĂ‚ÂÂĂƒâ€¦Ă‚ When I started out in NToV it was almost a guild joke that the Beastlords would be dead pretty much as soon as we engaged the rampage mobs. Jeido would call for the attack, Medes and I would send in the pets and begin our attack, then a few seconds later chat in the THF zone because we were dead before the first heal could hit us. Gear and AAs made the difference there (I like to think some skill development helped as well).
Do I think my pet is underpowered, yes. Would I like to see it changed so as to not take as much damage. I am not certain. It would make my life easier, save me some mana, increase my DPS output. However, I tend to feel that the weaknesses in the pet are part of the deal in running a pet class. My skills in managing the pet, being in the right group to provide support for the pet, and being able to control the pet during the fight, are the challenge that I like to try and beat. I havenĂƒÆ’Ă‚¢ĂƒÂ¢Ă¢â‚¬Å¡Ă‚¬ĂƒÂ¢Ă¢â‚¬Å¾Ă‚¢t observed how others control their pets in raid situations, so I really canĂƒÆ’Ă‚¢ĂƒÂ¢Ă¢â‚¬Å¡Ă‚¬ĂƒÂ¢Ă¢â‚¬Å¾Ă‚¢t say if I am doing it differently, but I have to say I donĂƒÆ’Ă‚¢ĂƒÂ¢Ă¢â‚¬Å¡Ă‚¬ĂƒÂ¢Ă¢â‚¬Å¾Ă‚¢t just send the pet in at the start of the fight then worry about my other DPS options. I am constantly sending pet commands to move him around. Back off from the fight, hold and wait for heals. Sending him back once he gets the heals. Making sure he is positioned behind the target, and so forth. I used to try and run my mage and my bst at the same time but it was a disaster since the pets required so much management during fights. I often have a tough time boxing any of my other characters since the bst really is not a toon I can set on autopilot.
Just some observations.