I never thought about it but maybe I should advertise my two little private guilds for those under lvl 80. Then atleast more ppl could have a chance to find a grp within their lvl range. With 2 accounts, both full, I have toons of many different lvl ranges that could group with lower lvls.
Joining a guild I think is your best bet. Check the guild boards in the guild lobby and see who is recruiting for your game play. Haning in gl and /ooc LFG... doesnt really work as most are either afk or getting buffs after dying and heading back to their group. General chat is a good place to LFG as was said, avg of 200 are there. Also you can see what loot is rotting and get in on some of that as well!
As for mercs... well some ppl love them and others will not grp with a merc in grp. One thing is for sure, mercs arent always reliable. I have died and seen others die with a healer merc in grp. Mercs seem to take a lunch break at the worst times! Also a tank merck if not set right can run off and attack and get the whole grp killed. Mercs are a tricky thing and not 100%. Also if you are tagged as the Puller, the healer merc wont heal you. Not sure why they made them that way but there it is. Supposedly when you tag a MT & MA the melee mercs will assist the MA once MA hits mob. Well I have seen mercs just stand there and do nothing more times than I can count. And its not because the merc is set to passive. My own mercs have done this.
All my toons own a merc BUT I
always use hot keys to control my mercs. With my tank mercs I always set them to passive when someone is pulling and once a mob is engaged I set merc to assist. My rog merc is always set to assist unless I see it acting weird then I start using my hot keys. My cleric mercs are always set to reactive unless there is more than one in the grp.
Ive grp'd my wiz with my necro and 1 healer merc and 1 tank merc and they owned the zone. Ofcourse they are only in their mid 50's atm but still. My shmn w/ healer merc grps with my war w/ rog merc and they do pretty well also. They are 88 & 83 both with t5 mercs.
Dont count on a grp getting rid of their merc for you either in a grp. Sometimes the grp needs the merc because its the only healer in grp or many times they dont want to share the loot with others because they are boxing 3 toons w/mercs.
As for the usefulness of a merc at higher lvls well if the merc is t5 then it is great. I have seen t5 mercs be MT for grp and grp did very well if the merc was the higher lvl. I have grp'd with MT mercs and taken agro from them just because I was 3 lvls higher so my dots were doing more dmg than the merc.
So there it is...