I've got as far as The Temple of Mythal, well of sorrows. I've enjoyed the game up until now, but it's suddenly got really hard, I had to leave a quest with a dragon in the desert because it just wiped my out every time, and now Samson just makes mince meat of everyone, not matter what I try. I've put the gamplay down onto 'casual' and keep having to run away and revive everyone, but still get killed. What was a really fun game has just turned into button mashing frustration, and I seem to spend most of my time looking at the bar on the bottom of the screen, waiting for powers to recharge, than actually seeing whats going on. Give Am I doing wrong?
frustrated.
Hard to give advice without knowing details: XP level, who is in your party, what specialization and focus abilities they have, gear levels, etc., etc., but here is some generic advice.
Preparation
Presumably you have a save after coming through the doors at the place where the resupply cache is. If you have one further back, make a save at the resupply cache.
Restrict access to health potions. Non-essential/low damage dealing characters or characters that don't need much healing should have a 5 potion reserve (8 if you have 12). That keeps your weak characters from sucking down all the healing from your strong characters.
If you have any S&S character with decent armor, set their one preferred skill to be Shield Wall (preferably upgraded) and set the AI to Follow (Self), so you can send them in to keep Samson occupied. If that same S&S can also Taunt, with Challenge preferably, set that to Preferred also and target Samson. The idea is to keep Samson's attention focused on someone who is going to deflect most of the damage done to them.
I don't remember if Samson has Perceptive or not -- if he doesn't and you don't have an S&S, you could use a DW Rogue instead and make Stealth and Flank Attack preferred skills (preferably upgraded to put you back in Stealth), Follow Self, and send them in to keep Samson busy.
Set everyone's AI to Follow (Self) so that they can independently target different enemies.
General tactics
Send your aggro soaker (see above) in to attack Samson. Everyone else attack (from range, if you can) the red templars with him until they are dead -- if the adds (additional enemies) show up deal with them at range also, more or less ignoring Samson. If I recall correctly those first red templars are vulnerable to fire, so use those attacks if you can.
If you have grenades, particularly Antivan Fire and Bees, use them on Samson.
Once the adds are cleared, focus all attacks on Samson. Hopefully, you befriended the Guardians so you'll have some help, but if not, Barrier and Guard generation (any warrior have Horn of Valor?) are your friends.
Use Pause or Tactical as much as necessary. You can anticipate some of the big damage attacks and get out of the way with evasion skills, or cast protection like Barrier or Horn of Valor. Stay away from Samson, except for the aggro tank. Keep moving around the battlefield.
When the weaker non-essential characters die, don't rush to revive them. You can leave them dead the whole battle if they are a net liability. You only need one strong character to finish this boss, so be ruthless.