What changes to the ranger should be made to make it a viable class in 5e?
There was a great article that said that the Beastmaster was bad because the familiar was extremely fragile, and that buffing the familiar's abilities (death saving throws, further HP and AC improvements) is necessary to make it good.
So what about the other ranger path?
Hunter Ranger is fine.
Beastmaster is simple:
>Beast follows the action you commanded it to until you tell it to stop or do something else
>HP is 6 * ranger level instead of 4 * ranger level
>outright state that it's proficient with light and medium armor as barding
>7th-level feature gives the companion magical attacks
>your proficiency bonus adds to the companion's save DCs for wolf bite, poison, and so on
Due to the way cantrips scale (with total character level) and the way rogues deal damage (one big pool of sneak attack damage per turn), green flame blade is a flat damage increase with no downsides if you get access to it.
I wouldn't call it OP, but it's definitely The Most Optimal Way to Play a Melee Rogue at this point
>Let them have Great-Weapon fighting style.
>Pets scale better, get magical attacks at level 7, they act on their own initiative.
>Add Spell-less Ranger that actually has decent abilities