The will of the king cannot be simply gauged by the concept of tactic. Saber believes the only way to stand a chance against him is to take him down before he gets serious.

Q: Who is stronger, Gilgamesh or Arcueid (30%)? While Arcueid has the strength of 4 Servants, I remember there being a scene in hollow implying that Gil was the equivalent of 5 Servants + a.
A. In the definition of Arcueid's strength, there's this thing where "her output changes according to her opponent". As an absolute order taken from her backup, the planet, she is allowed only an output a little stronger than her opponent. А. Single entity abilities of Arc and Servants are roughly on the same level

Servants use their respective Noble Phantasms while Arc uses her unlimited backup to fight, and differences occur depending on affinity. A simple-is-best Arc is an all rounder, and so generally her chances of winning are only high, but there are those opponents that she just has helplessly awful compatibility with.

For example, in cases where even if the guy's stats are about the same as Arc, he has a ridiculously large number of weapons with high versatility. As the amount Arc is allowed to take out is based on "single entity ability", against types like Gil-sama, well, you see?

And the "5 Servants + a" line is a comparison of simple "firepower". Like with the "corpses", foot soldier level opponents aren't going to be avoiding their attacks, so the ones who'd have the advantage are the ones who have more weapons. The reason why Servants excellent at one-on-one combat didn't stand out in Broad Bridge was because of this. Also, for normal Arc, she would get approximately the equivalent of 2 Servants single entity stats.