Feel free to add more to this list, these are what came to me off the top of my head. Hopefully putting the bugs and issues in one place makes it easier for Zenimax to identify the issues and fix them.

1. Nirnhoned 2h weapons + Light armor providing nearly 100% spell penetration and bugged bonus damage
-Check to see if this has been fixed and that nirnhoned gives the correct amount of spell penetration

2. Radiant Destruction (and morphs) having no counters (purge, cloak, cleanse, etc.)
-Check to see if this ability can now be countered by purge, cloak, cleanse, etc... as can other channeled abilities

3. Unbreakable CC caused by getting hit with an immobilize and hard CC at the exact same time, or multiple CC's at the same time
-Check to see if "break free" works or if permanent unbreakable CC remains in the game

4. Unresponsive controls due to hitting light attack or left mouse button just before issuing a command
-Check to see if the game still ignores commands shortly after pushing light attack/LMB, making the game feel unresponsive, or if this has been improved. Simple test is to hit light attack/LMB and then hit weapon switch right after within a few miliseconds. In 1.6, the weapon switch will be completely ignored.

5. Unplayable Cyrodil Lag
-Check to see if groups of more than 8 people vs 8 people cause the game to start ignoring player inputs and causing lag

6. Unresponsive Controls While Being Focus Fired in PVP
-Check to see if more than 3 people are focus firing one player in a pvp scenario, including throwing soft and hard CC's, the game begins ignoring up to 50% of the targeted players actions, as if they never even pushed the buttons.

7. Missing Alliance Indicators and Healthbars
-Check to see if alliance indicators randomly disappear, making it extremely difficult to distinguish friends and foes in PVP.

8. Health Bar Desyncs
-Check to see if shielding yourself multiple times with different damage shields, having them be destroyed, and reshielding, causes your health bar to bug out and become unreadable. Also check to see if DK's and Defensive Posture reflecting your attacks causes your health displayed to be inaccurate

9. Champion Traits Not Working Or Not Showing On Tooltips
-Check to see if the armor you get from the armor talents actually reduces incoming damage, it didn't in many of the previous patches
-Check to see if healing bonus "blessed" improves healing from momentum, vigor, and purge(cleanse), the tooltip doesnt change.
-Check to see if "healing recieved" champion talent improves healing taken from momentum, vigor, and purge(cleanse) at all
-Check to see if "mighty" improves base damage and crit damage almost as much as crit damage talent improves only crit damage
-Check to see if the DOT damage reduction champion talent reduces damage taken from channeled abilities, or if its even intended

10. Rally often does not heal at the end of its duration
-Check to see if the bug has been fixed