While I agree with Otcho in principle, I would like to attempt to illuminate some nuances and concerns I have regarding changing the current system.
Pets despawning because of FD is the easiest place to start, so-- ON LIVE, for a while, player pets could aggro kos NPCs. Some enterprising Necromancers, such as a good friend I knew, would beef up the pet by giving it fine steel daggers, or ykeshas (psycho), then flop in key areas of lower guk, and go to bed. Overnight, the badass pet would dominate the 3-5 frogs in the area as they respawned, and my buddy would wake up in the morning with tons of xp/aa's/faction etc. Fun little gimmick for live, but not the kind of gameplay I would like to see on our server. I have /no/ idea when pets were changed in WR/SoD so that they do not aggro mobs, but I believe the original proposition for having pets despawn after their master has been FD for x amount of time (4 minutes?) was to curb this kind of gameplay. Perhaps I'm wrong here, and someone with a longer memory can chime in, however I believe this is a key solution for preventing abusive gameplay. And it's worked-- for nearly ten years (or longer). Yet, with the advances all the different developers have included over the years, the current time limit seems a little bit too draconian. I've only been back playing for four months after a 4-5 year hiatus, but if I remember correctly, it should take a successfully FD character no longer than 2-2.5 minutes before ALL mobs have reset (including roamers). Correct me if I'm wrong, because I'm making the assumption that this is still close to accurate. However, this only leaves 0.5-1.5 minutes for the player to stand up and either FD again or move to a safe spot to save their precious companion and all the toys he paid good money to give to it. This seems unnecessarily difficult for some players, especially new players to the server. Or maybe it's not that difficult an idea, and players should just suck it up and be better. Part of me feels that way, because these kinds of checks on the power of players are fundamental to the foundation of the server.
What the solution to this problem is, I'm not sure. Perhaps extending the FD grace period before the pet despawns. However, I would be very conservative with the increase in time to maintain a pet while FD--Maybe another minute or two? I think the notion that pets should never despawn due to the player being FD for x time is too big a change to make without a lot of oversight and balancing. I play a Monk, so I have very little skin in this fight -- however, some things to consider: Froggy's Jar, Small Iron Cage, any other "mini" pet that I don't know about who could theoretically give a player, or group, unlimited boons while it's master is FD and afk indefinitely. There's more at play than just Necromancers being frustrated their pet is gone with all it's cool stuff.
The second issue-- experience penalty for flopping a mob after you have been the majority damage dealer to it. Succinctly, this was to combat the nappy scumlords who would use their high level monks to beat mobs down to 1% hp, then flop, and allow their un-grouped, SIGNIFICANTLY LOWER LEVEL twink/alt/buddy to get the killshot and earn tons of xp for killing a mob normally way out of their league. I vividly remember watching a select few monks do this when I first started playing, oh so long ago, and thinking although it's clever, it's still a pretty trashy way to powerlevel/play this game. To that end, I'm all about preventing that kind of gameplay from returning. However, this fix resulted in a new issue that Monks, and Necromancers have to deal with: (quickest scenario) you are a Monk or Necro in a legit exp group, and you are the best dps there-- if you pull aggro away from the tank, the fastest tool to wipe aggro and return the mob to the tank, is that Feign Death button. It's not the only solution, but certainly the easiest, and the most reliable way BY DESIGN. If you were the majority damage dealer to that mob at the point you successfully feign death, and the mob's hp is significantly reduced (30-40%?), when the mob dies you will receive an Assistance Penalty upwards of 90+ percent towards experience gained from the mob. Essentially robbing yourself and your group members of the very thing you were trying to collect in the first place.
The current system that is in place to prevent abuse of the FD mechanic has repercussions against legitimate uses of the skill, because it does not differentiate between abuse and legitimate gameplay. This is something that can be endlessly frustrating when it happens, because despite your best intentions, and playing the game completely within the rules, you can be arbitrarily punished for using the skills provided to you for the exact situation for which they were designed.
This is admittedly a very niche issue, combined with potentially difficult fixes to alleviate the concerns. I'm not advocating this be immediately addressed, just trying to give perspective and context to what Otcho suggested in the OP. I would rather deal with losing some xp because I fat fingered a hotbutton (or let's face it, for being a terrible player), than suggest reallocating limited resources to a problem that is not endemic to the playerbase at large. Yet please understand my point that it is absurd to have to play a meta game within a fantasy world where I have to worry about weather or not the system will mistakenly think I am cheating and punish not only me but my friends I'm grouped with. Eventually we can come up with a more elegant solution that addresses both concerns.
Damn this turned into a long post. Admins/Devs -- maybe look at this again later when you have time to read a wall of text from a player who is trying to explain some weirdness they face when playing the game.