Timewalking isn't as bad as retail dungeons but you may as well build around the same idea of having every tool you need in your toolkit. All the important ones anyway.

Dispels for all curse / poison / disease / magic
High mobility specs
Snares
Stuns
Incaps
Interrupts on at least 3/5
Good wall / recovery abilities
Battle rez

Those are the most important off the top of my head. The e-sport direction dungeons are going is brutal and you need a well rounded team and some excellent mappings to make it enjoyable. Definitely don't do what I did making a meme comp of your favorite specs only to find out you're missing important debuffs, mobility, etc.