[Aerich]

1) It's ok, I guess. I personally wouldn't have my only cleric be a) a 3 ECL race and b) a decoy. Part of the greatness of a Dreadmaster is highly effective enchantment spells, which it cannot cast without risk if it's sitting in the frontlines.

2) I don't think the ranger class adds anything here. I'd rather have the extra 3 levels in illusionist, especially as you would be able to start progression in the spellcasting class sooner. Use two of your fighter feats on the dual-wield feats if you really have to.

3) It's ok.

4) Fine. Why 15 in Dex? Are you planning to add to it? I understand the uneven Wis (Pally bonus stat will bring it up), but the Dex has me mystified. If you add the extra point to Int instead, you could take Expertise if you want it.

Some additional comments on party structure:

I understand that you want a powerful party. What I don't understand is why it is so uneven. It is generally unnecessary to have two decoys, and it's downright strange in a 4-character party. I'd prefer to replace a decoy (probably #1) with a stronger cleric (no ECL penalty) that is better in offensive melee - e.g. a dwarven Battleguard. The party is severely lacking in arcane support, so I'd make it a priority to develop #2's spellcasting ability sooner.

Realistically, you have a decoy, an underpowered cleric/decoy, a support character, and a bomber. That's three characters devoted to making an effective meatwall, and one character devoted to killing stuff. If you are committed to carrying only 4 characters, I'd strive for a better balance. If you intend to add additional characters (e.g. two out of three of a backline cleric, wizard, and offensive meleer), the current balance is ok.