>>72377742This is completely normal for a first time run. Iceborne is designed so that you're always facing the major milestone monsters with a gear deficit that drags out the clear time--because they wanted to encourage players to party up.
Tigrex is one of the most extreme examples, because it naturally presents limited DPS uptime compared to other monsters around the same stage of progression. If your damage isn't high enough to effectively kill it within the guaranteed windows presented by your crowd control tools them you end up spending a considerable amount of time just chasing its tail or countering its charge for tickle damage over and over.
