My initial take on this is that you got some overanxious/trigger happy DPS in your groups. Being a Prot Warrior, we typically draw the first of the blame unless it's blatenly obvious that it's someone else's fault.
But, that little opinion aside, I'll get down to your questions.
Issues 1 & 2: Yes, typically the DPS needs to hold off a few seconds while you draw aggro. Typically I like to go in with charge, thunderclap, and then start my usual rotation of Shield Slam, Devistate, Revenge, Cleave, etc, etc, etc (while cycling through targets with Tab). Always start off with Shield Slam because that is probably your highest threat generator right there and with Sword and Board, Devistate and Revenge both will have a chance to produce it multiple times.
Issue 3: Demoralizing Shout, IMO, is not that great of an attention getter. Taunt and Mocking Blow is usually better while cycling through targets. Failing that, pop Challenging Shout (which I like to keep on cooldown for just such an occasion) to get everyone's attention.
Issue 4: Healing Problem? Yes and No here. Without being there to see what's going on, I really can't say either way for sure what's happening. I hate to state the obvious, but, healer's responsibility is to keep you alive first and everyone else second.
Issue 5: This is not really an indicator that you are the problem. I've seen high tiered Tanks blow a raid or two and I've seen low tiered Tanks handle aggro with the best of them. That, and everyone is entitled to an off day. I had issues one day with H ToC and couldn't tank the champions to save my ever-loving soul. LOL.
Issue 6: Again, can't really tell without actually being there. I will say that being in a guild should be more about a friendly atmospehere than about finger pointing or having blame-a-thons about who's a problem duing groups and/or raids.
A problem in a guild should be something like personality conflicts, ninja looters, Guild Bank Thieves, or something like that. A problem should not be "so-and-so isn't pulling their weight as a healer/tank/dps/gnome/troll/whatever". Running Guild Heroics and Raids should be a growing and learning experience for everyone. It shouldn't be about completion or acheivements (although they are nice perks).
For example; My guild on Kirin Tor wiped on Heigan in a Naxx10 run because one of our tanks was demonstrating something to me to help me tank and accidently aggroed him. Another example is when my wife (who's a Hunter) used disengage from the Lava Elementals to fly backwards UP the stairs in H HoL and ended up aggroing both of the mobs up there before we could mow down all of the elementals. Heck, I got overzealous on a H CoS run one time and ended up aggroing the whole gauntlet and blowing a timed run for some guildies.
I could go on forever on examples from just my guild alone. . The point is that the guild shouldn't self destruct because of a few wipes because someone is new to 80, or learning a new class, or needs some pointers, or whatever. Guilds should be helping everone else out where they need it and they should be patient and understanding if someone is having problems and needs a hand from time to time.
Alright, I'll get off the proverbial soap box now. I hope that this helps ya.
"Incoming Fire has the right of way"
-Murphy's 18th Law of Combat