I made some statistics using Raidbots data (all parses, last 2 months).
10N (samples 89,840)
Fire ..... 47.9% ..... (43,014)
Frost .... 45.9% ..... (41,273)
Arcane .... 6.2% ...... (5,553)
10H (samples 17,047)
Fire ..... 73.5% ..... (12,537)
Frost .... 21.2% ...... (3,611)
Arcane .... 5.3% ........ (899)
25N (samples 47,643)
Fire ..... 57.9% .... (27,609)
Frost .... 33.4% .... (15,915)
Arcane .... 8.6% ..... (4,119)
25H (samples 23,844)
Fire ..... 79.9% ..... (19,047)
Frost .... 10.2% ...... (2,439)
Arcane .... 9.9% ...... (2,358)
25LFR (samples 40,580)
Frost .... 53.9% ..... (21,877)
Fire ..... 27.3% ..... (11,083)
Arcane ... 18.8% ...... (7,620)
There are a few things I don't understand:
1) Arcane is ranked higher than Frost in all except LFR. Yet Frost has way more samples. Why?
2) Arcane seems to be more popular in 25m raiding. Why?