Scathis essentially removes the uniqueness of UEF Mavor experimental: the only piece of artillery that can reach the entire map
Scathis has half the range of a Mavor now (in the vanilla version it has the same range as a Mavor btw).
Also that aspect of Mavor is not really what makes it unique. It's the high damage and high accuracy that is most important.
Scathis was fine being a beast in the mid-short range
If by being "fine" you mean completely worthless and never used then you are correct.
Salvation has the same problem; it was fine being a quick shooting arty with t3 range
Salvation was not changed at all in that regard, what are you talking about?