Hardcore Mod v1.4 - - [works with saved games from v1.2 and higher]
Lyrium dust is now unusable
Minor spell cooldown and mana cost tweaks
Hardcore Mod v1.3 - - [works with saved games from v1.2 and higher]
Hard* difficulty is now the same as Biowares nightmare difficulty (*Playing on hard is recommended)
Nightmare difficulty is significantly more difficult
Lyrium potions, health poutices, and injury kits are not useable
AI improvement: enemies will use powerful abilities more often
All enemies have an innate 35% resistance to all spells
Requirements for spells have been changed to a level based requirement
The mana cost and cooldown of all spells and the mana pool of a mage has been significantly altered
Some spells have been removed (they can be skipped while leveling up that tree)
Players no longer gain small amounts of health, stamina, damage, or defense upon leveling
25 tactic slots per character
Rogues gain a skill (not talent) every level, warriors every 2nd level, mages every 3rd level
All shapeshifting is done immediately
As a note, it is recommended to play with the dagger hot fix until bioware official patches it. You can find that fix here:
http://dragonage.gulbsoft.org/lib/exe/fetch.php/hotfix/dexterity_fixes3.zip