After reading through all the posts here, there is one thing that nobody mentioned. The fact that everyone playing this game pay their money to play it, therefore they choose how they want to play it. I understand that some people have been hindered by the addition of mercs due to lack of groups, but for others, it has been a great addition to allow them to explore the game more in depth while still playing how they want to, being solo.
While EQ is a social game, that doesn't necessarily mean that you have to group to be social, chatting with people in chat channels is just as social as chatting with them in the group channel. I used to love grouping with strangers, getting to know them etc, but as the game has gotten older (and myself in the process) I have found that the game can be much less enjoyable at times by doing this. Getting into groups that have... let's say, less than educated people just destroys the fun in the game for me. And there are many different ways this can happen, such as the hotzone only players that have leveled so fast, they have no clue how to play their class. Experience mooches who are busy watching TV and at best turn auto attack on and look away. There are so many things I can list that just annoy me while playing that I find it worthless to bother with.
Then you get situations where you are trying to get an item for your toon, or an alt. If you can take this mob with your toon(s) and mercs, this provides more profit for your time involved, rather than camping for hours on end, just to have to roll against others who have no use for the item other than to sell it in bazaar, whereas you are trying to get the item to not have to PAY people like that for that item.
All in all, I feel the mercs are a great addition to the game. It has opened many doors for people to enjoy the game in more ways that provide more enjoyment for them. I do feel a little bad for some people missing out on some groups, but at the same time it is no different than the warriors missing out on groups for years because so many other classes can do their job as long as the mob isn't a raid mob that defensive is required, or wizards/druids losing out on jobs years ago when PoK was added, making the benefit of a porter becoming a non-issue.
In the end, if you truly feel the mercs have ruined the game, think back on how you have played the game and look at features you have used that make the game better for you, and realize that most likely that feature has caused issues for somebody else in the past. Not everyone can be pleased all the time, and in the end, we all have the ability to cancel our accounts if the game has been ruined for us.