All of the tiers seem to be really active lately. I'm sure that we can get something going anywhere.
The basic strat for both BO and Keeps is to zerg.
Attacking a keep:
-If you're attacking a keep, it's most important to protect the postern doors to keep the destro from sneaking in.
-Defending teams have a huge advantage (choke-points, extra buffs, extra NPCs, etc). If Destro have a group inside a keep that is 50% the size of your attacking force, they can probably stop you from taking the keep. Obviously, it depends on class make-up and how well they work together.
-When attacking a keep, take out the oil and any balista as quickly as you can.
-Never stop in the doorway. The people behind you will get killed if there is still oil up.
-Once the doors are down, make sure everyone gets into the base of the keep and move up as a group.
-Make sure you have someone with a knockback effect ready so you can dislodge a tank wall.
-NEVER STOP ON THE STAIRS.
-As a healer, try to heal everyone, even if they're not in your group/warband.
Defending your keep:
Obviously, the reverse of all the above holds true when you are defending the keep.
-AoE classes (Bright Wizards, mostly) can stand out of Line of sight and rain down fury near the ram in some keeps.... practice! Combining Rain of Fire with Oil can be devistating.
-Duck in-and-out of sight when attacking from the ramparts. If you can see them, they can see you. DoTs will kill you if you're not careful. Get used to ducking and running in-and-out while throwing dots into the crowd when possible.
-Once the doors are all down, have your tanks stack up on the top of the stairs and have everyone else AoE on top of them. You'll mow down a lot of people. Even if your group is significantly smaller, you can hold the destro up a looooong time and farm tons of XP/RP/Influence from them.
-There are a few good places to sit as a healer in each keep so you can heal your tank wall. Go explore before the destro are there and figure out the safest places that you can stand. Watch where the DPS people stand - they'll be able to see the stairs.... and your tanks.
-Rez other rezzers first. Basically, recruit help. Tanks should be your second priority. Then worry about rezzing DPS people.
-Healing vs Rezzing: Tricky to manage. Basically, you have to decide if letting whether it's more important to rez Player2 or heal Player1. It's situational awareness - sometimes you need the tanks back up to hold the wall. Other times you have enough tanks and healers...so rez the dead.
-As a healer, try to heal everyone, even if they're not in your group/warband.
If you play an ArchMage, you REALLY need to take the talent that gives you an instant rez. I can't even begin to explain how valuable that is for oRvR. Even if you create a new group of talents... you need to have one pre-set with this.
Anyway... just a quick list of things I try to think about on my toons.