ΔE 15.4, loose: different enough that you should pick on purpose. Dark Elder Bronze is noticeably darker than Warplock Bronze.
Can I use Dark Elder Bronze instead of Warplock Bronze?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Dark Elder Bronze is noticeably darker than Warplock Bronze.
Can I use Warplock Bronze instead of Dark Elder Bronze?
The same difference applies the other way round: Warplock Bronze is noticeably lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.