I've deleted my initial answer and have taken a 180 degree turn on this.
First let me layout what I think the chords are...
D#m7 B(sus2) E(sus2) F#
...with the melody working around F# G# A#
.
D(maj7) E(sus2) F# Bm(sus2)
...with the melody working around F# C# B
descending back to F#
.
I think that's roughly what's happening.
IF I have those m7
and sus2
chords right, then the whole song has F#
and C#
sustained throughout. Combine that with F#
major being the only plain major chord and it makes a solid case for a tonic of F#
.
Now, about the E
chords. The sound like the third is omitted and replaced with a second leaving them sort of ambiguous in terms of major/minor. But, in the melody there is a G#
which would be the major third of the E
chord if they weren't sus2
. So, the implication is E
major. Now it seems pretty clear both sections have E
to F#
as bVII
to I
.
In the verse it's a vamp between D#
and B
ending with E
to F#
. Roughly IV bVII I
dressed up with suspensions.
The refrain is essentially D
, E
, F#
as bVI bVII I
.
The song gives two presentations of bVII I
where I
is rhythmically shifted by a bar and the submediant is a borrowed chord in the refrain as a way to differentiate the two sections.
I still to my point about pop music and key ambiguity. This verse would probably be notated with an F#
major key signature and accidentals for bVII
. The refrain sort of shifts to minor, but it might be just as well to use a F#
major key signature and accidentals so that the borrowed chords are high lighted as such. This where I think it might be best to say it's nominally in F#
major in terms of key signature but not in terms of major/minor system cadences defining a key.