No 8 Tiatia struck from close-range with five minutes left at Ravenhill to keep up the pressure on leaders Munster.
And Wales star fly-half Hook claims the 16-13 victory was a massive confidence boost for the region following last weekend’s EDF Energy Cup semi-final loss to Gloucester.
Hook said: “It was a hugely important win not only for our league hopes but to regain our confidence – we showed real bottle to fight back and win the game.
“We dominated the game but we knew it would be difficult to get back in the game after conceding a late try.
“It was a real team effort and that paid off in the end but Filo is a big-game player and a massive presence on and off the field for us.
“We just have to keep winning our games and put the pressure on Munster – it’s a massive boost for us.”
The Ospreys now face a Heineken Cup quarter-final showdown against the reigning champions in Limerick this Sunday.
