IME, and I stress IME (which may be very skewed given the psychotic nature of my RBDM), every character needs to have some survivability to them both individually and as a group. In my DM's version of RttToEE every battle is about 4 or 5 CR increments above our average party level evinced by the fact that we use absolultely all of our resources every battle and are lucky that we win. And when I say lucky, I mean it. I find it truly unbelievable that our DM is not rigging the dice in our favor sometimes for how lucky we get - a failed smite good here, or a missed save there. But when we question him he just starts rolling all the dice in front of us, and it is...well just plain luck
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Our current party consists of:
human Cleric 6/Radiant Servant of Pelor 4 (me)
half elven Paladin 5/Templar 4 (of Heronius)
dwarven Fighter 1/Psion 9
dwarven Barb 1/Ranger 1 (3.0 version)/Fighter 8
We buff similarly. BTW, prayer and recitation don't stack - they are both luck bonuses. Moreover, I am amazed you are not preparing Protection from Evils or Magic Circles. Those spells have singlehandedly saved our party SOOOO many times.
Anyhoo, what I have noticed in our group is that we suffer from two things: we are hosed on reflex saves and we have no arcane magic (the psion is a very poor substitute - GOD psions SUCKKKKK) - but that rant is best left for another time. The reflex saves we try and boost with Protection from Evil and Recitation and Eagle's splendor for the paladin. What has really saved us though is that every character is incredibly tough. Our saves are all awesome, especially when buffed and hp's are also all above par (well, maybe except the paladin but we always give him endurance, aid, and a shield other).
As a veteran gamer, I notice that our main drawback is not having any arcane offensive power. A few spells would be really REALLY nice:
Invisibility!
HASTE! (even with the nerfed version)
Magic Missile
and many more. I would say go with the arcane caster just to get Haste, just look at it like this - everyone can make an extra move or attack. Mobility is everything with that game - it is the priests only real flaw. Let your increased threatened area-monk act as the wall while your druid and archer pick off people and you counter spells. Hasting your party giving all those PCs and summoned animals extra attacks will be REALLY worth your while.
However, as I mentioned, every character needs some survivability - at least in my DM's sick twisted game. I would never build a straight caster in that game! 10d4 hps + con is just begging for a one hit kill. More importantly, once that wizard makes himself known with one 5th level attack spell, he will be the primary target end of story. You simply can't outrun a fireball
. I'd say make a mixture of a melee/caster build. I have been working on such builds for a long time and had the penultimate version (I thought anyway) until 3.5 busted it all up with eldrich knight. Now the build is: Sor 4/MotAO2/Pal2/EK9/Sacred Exorcist 3. Buff the sheite out of that charisma, give him divine might feat, power attack, arcane strike (IIRC), expert tactician have him wear platemail and take the still spell feat. Have him select only a very few attack spells and the rest selected from things like true strike, and other nice buffs (haste of course). With MotAO, he will be able to cast any 1-3 level spell. He has extra spells from Sacred Exorcist, his chr adds to his saves, and he can wear uber armor. He should be VERY survivable. His spell offensive power at that level would only yield 4th level spells. However, he could provide all of those very nice wizard buffs that you are lacking in - blink and haste to name a few. A blinking rogue would be quite nice.
This character's real weakness will be in spell resistance. But let the cleric and druid take those foes on and he can switch to melee and be an additional buffer. Alternatively he can be the counterspeller - which is also a much needed niche in our group, despite my cleric.
Anyway, hope the cohort works out. BTW, don't overlook all those other followers you get. At 12th level I am sure you are aware of the dwarven clan that used to occupy the mines. Drawing from them is probably appropriate, but of course talk to your DM. A bunch of crafters is incredibly useful - I am planning on taking leadership at 12th for that express reason
.

Our current party consists of:
human Cleric 6/Radiant Servant of Pelor 4 (me)
half elven Paladin 5/Templar 4 (of Heronius)
dwarven Fighter 1/Psion 9
dwarven Barb 1/Ranger 1 (3.0 version)/Fighter 8
We buff similarly. BTW, prayer and recitation don't stack - they are both luck bonuses. Moreover, I am amazed you are not preparing Protection from Evils or Magic Circles. Those spells have singlehandedly saved our party SOOOO many times.
Anyhoo, what I have noticed in our group is that we suffer from two things: we are hosed on reflex saves and we have no arcane magic (the psion is a very poor substitute - GOD psions SUCKKKKK) - but that rant is best left for another time. The reflex saves we try and boost with Protection from Evil and Recitation and Eagle's splendor for the paladin. What has really saved us though is that every character is incredibly tough. Our saves are all awesome, especially when buffed and hp's are also all above par (well, maybe except the paladin but we always give him endurance, aid, and a shield other).
As a veteran gamer, I notice that our main drawback is not having any arcane offensive power. A few spells would be really REALLY nice:
Invisibility!
HASTE! (even with the nerfed version)
Magic Missile
and many more. I would say go with the arcane caster just to get Haste, just look at it like this - everyone can make an extra move or attack. Mobility is everything with that game - it is the priests only real flaw. Let your increased threatened area-monk act as the wall while your druid and archer pick off people and you counter spells. Hasting your party giving all those PCs and summoned animals extra attacks will be REALLY worth your while.
However, as I mentioned, every character needs some survivability - at least in my DM's sick twisted game. I would never build a straight caster in that game! 10d4 hps + con is just begging for a one hit kill. More importantly, once that wizard makes himself known with one 5th level attack spell, he will be the primary target end of story. You simply can't outrun a fireball

This character's real weakness will be in spell resistance. But let the cleric and druid take those foes on and he can switch to melee and be an additional buffer. Alternatively he can be the counterspeller - which is also a much needed niche in our group, despite my cleric.
Anyway, hope the cohort works out. BTW, don't overlook all those other followers you get. At 12th level I am sure you are aware of the dwarven clan that used to occupy the mines. Drawing from them is probably appropriate, but of course talk to your DM. A bunch of crafters is incredibly useful - I am planning on taking leadership at 12th for that express reason
