Go vertical, or redesign.
Exactly. If you need to redesign it in order to change scales to any significant degree, then it isn't scalable design.
It actually is scalable design, not a leftover. A primary driver of the indicator size is too not block the portrait.
Ok, sure, it could be not to block the portrait.
That isn't scalable design, that is just trying to make the UI unobtrusive.
Secondary is for available space to be divisible by the indicator size.
Ok, so it just happens that it turned out to be able to fit 4 number cards in there before they would be too small. That's still not scalable design when the only scalability is an increase of 1 before having to redesign.
It's just a convenient little extra left over from other design decisions.
like that (and you're assuming that spacing is the most important goal, which it wasn't). In actual game development you have to find the balance between scalability vs time/effort. The UI isn't web based or made with standard tools, it's proprietary, and something that seems simple may be significantly more time consuming than you would imagine. You design within the constraints and plan for future scaling as best you can.
Except that they've already done basic UI element scaling in the game.
In duos, the bottom bar is filled entirely with two players. The nameplates get scaled up or down to fill out the bar depending on the number of players.
Red shields have their shield pips scaled down so that the overall bar is the same size as a purple shield bar.
They are by no means incapable of scaling elements to fit requirements.
The bottom nameplate bar is set up to be scalable to a decent degree with the width of the nameplates dynamically changing.
The legend portrait area is set up to be scalable to a great degree, since they planned to add more and more since the start.
The numbers on the portrait really aren't scalable, there is just one single little space left over that may come in handy, but hardly counts as being scalable design.