Not trying to talk you into pre-ordering the game, just wanted to say that we were very aware of Hard West's flaws while working on Phantom Doctrine and I like to think that we've done a great job avoiding those. Since obviously quite a few people (not just here) have brought up Hard West and drawn comparisons to it, I'd like to go over a few of the big changes:
One of the design decisions that really bit us in the A were the reaction shots (automatic 100% hit when getting close to an enemy), those were replaced by a very nice overwatch feature where you and the AI can actually choose what area to cover. No overwatch: okay, safely walk up to the enemy and shoot them in the face or perform a takedown.
In Hard West many characters were plot-related and losing them resulted in instant game over. In Phantom Doctrine all characters besides your avatar are allowed to die and you can even lose entire missions without losing the game (certain missions have to be won, of course).
Hard West was divided into chapters and you regularly had to start over with a new team as you made progress in the campaign. Now you can use your favourite guys from start to finish.
In Hard West there was no saving during tactical encounters (until quick saving was introduced as an experimental feature in a patch) and only autosaving on the world map. This time you can save at any time and the game is also automatically saved each turn during tactical missions and at regular intervals while at the hideout.
Hard West's world map lacked a bit of depth and progress was quite linear. This time you have an actual strategic layer where you manage your many agents, research new tech, send your agents on various jobs to counter the enemy, launch many optional tactical missions etc..
One thing that everyone seemed to enjoy in Hard West was the Luck system that replaced random hit chances. The system returns in a new guise as "Awareness" and was greatly improved. Now it regenerates per turn and there are many ways to replenish it actively or attack enemies' awareness directly. Again it additionally serves as "mana" for using certain abilities and does so more effectively.
Another well-received thing was the "Setup" mode where you can move quite freely before engaging in combat. This one was extended into a full-fledged stealth mode called "Infiltration" where you can actively eliminate enemies and even finish entire missions without engaging in open combat.
These things are just the tip of the iceberg, of course. There have been zillions of other additions and changes, whether it's to the combat mechanics, mission design, character development, artificial intelligence or the presentation. Then there's of course the entirely new stuff like kidnapping hostile agents and brainwashing them, support powers (e.g. snipers helping out from outside the map), weapon modding, multiplayer and much more. It's safe to say that we've come a really long way since Hard West.
