Looking through the (1825) usage stats, the only common abusers are:
at 14.121%
at 7.294%
at 8.206%
at 16.701%
at 13.370%
at 85.782%
The usage stats were for an older metagame however. Using WCOP usage stats though
(only counts revealed moves iirc)
Round 2:
used Tera Blast in 1 of 38 games
used Tera Blast in 2 of 13 games
used Tera Blast in 1 of 2 games
used Tera Blast in 1 of 1 games
No other pokemon used Tera Blast in Round 2
For a larger sample size but older metagame, I'll use Round 1 too.
Round 1:
used Tera Blast in 1 of 272 games
used Tera Blast in 6 of 200 games
used Tera Blast in 6 of 102 games
used Tera Blast in 1 of 56 games
used Tera Blast in 2 of 47 games
used Tera Blast in 1 of 42 games
used Tera Blast in 2 of 32 games
used Tera Blast in 1 of 25 games
used Tera Blast in 1 of 24 games
used Tera Blast in 3 of 23 games
used Tera Blast in 1 of 18 games
used Tera Blast in 1 of 18 games
used Tera Blast in 5 of 11 games
used Tera Blast in 2 of 9 games
used Tera Blast in 1 of 2 games
used Tera Blast in 1 of 1 games