Title says most of it, but ill explain abit further.

When killing a foe or completing a mission, the experience gained it majorly just flashing by and very hard to notice.

fix either a slower animation for the experience or make a brighter color.

Er its fine how it is.
If you want to see it raise when you gain a level, look at what you have BEFORE completing a quest, then look what you have AFTER completing a quest.
Boom, profit.

Click the speech bubble tab to bottom right of your chat window. You can customize or create a new channel that excludes everything except reward information. that way you will always be able to see all the loot and XP you are getting.

Exactly this, i made a new tab called, rather originally, Rewards. This shows me all my resourses, xp and loot.