Stalkers are not bad as they are now.
Stalkers are just as worthless now as they were four and a half years ago when I first made this thread. They have not changed one iota since then.
complete invisibility will break the game.
Making the weakest specimen in the game with one of the weakest attacks in the game slightly harder to see would not break the game.
However, I would peg complete invisibility as a low priority adjustment as the change that Stalkers have really needed these past four and a half years is the ability to move while attacking, the same ability that Gorefasts, Bloats, and Scrakes were given back then. This single change would redefine the Stalker's role in its entirety, and it would be monumentally trivial to implement said change since it only requires a bit of copy and pasting from the fix that was given to Gorefasts, Bloats, and Scrakes made, once again, four and a half years ago. This change has
also been done by the community to great effect, so there's no shortage of established and fully tested references for what is essentially a 1 minute (if that) coding fix.
However, seeing as nothing has changed for nearly half a decade, I don't see Stalkers being balanced any time soon.