User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-1758220-20120411194739/@comment-3062343-20120411232035

My personal theory for Tigrex being absent is that people found it too easy in P3rd, what with the fixed hitboxes and stamina system. Tigrex barely had a change in moveset from Unite to P3rd, and those moves were pitifully easy to avoid without the 2nd Gen hitboxes. That, combined with the stamina system making him fall over after every charge when fatigued, giving loads of free hits to the head, made Tigrex pretty much a joke in P3rd. Narga didn't suffer as much from this, as (in my opinion) Nargacuga was more about hitting the player lots of times for relatively small damage, rather than one big hit that does huge damage, which works better with the 3rd Gen mechanics. I also never really found Narga's hitboxes to be particularly bad in MHFU, meaning the fixing of the hitboxes didn't really have much effect on the fight. My guess is that they left Tigrex out so that they can spend time revamping it for MH4.