This issue is caused by them renumbering and enumerating the Achievements in Legendary Edition, but forgetting to update the Unlock Condition to use the new AchievementID instead of the old one.
Specifically, in ME2\BioGame\DLC\DLC_EXP_Part01\BioUI.ini you need to find the [SFXGameContent.SFXGameChoiceGUIData_HenchmenPowers] header, and replace the line
+HenchmanPowerArray=(PowerClassName="SFXGameContentLiara.SFXPower_StasisNew",ChoiceEntry=(srChoiceName=127059,srChoiceTitle=127059,oChoiceImage=none,srChoiceImageTitle=127059,srChoiceDescription=365834),AchievementID=56,PowerImage="SB_Codex_Images.Stasis_512")
with
+HenchmanPowerArray=(PowerClassName="SFXGameContentLiara.SFXPower_StasisNew",ChoiceEntry=(srChoiceName=127059,srChoiceTitle=127059,oChoiceImage=none,srChoiceImageTitle=127059,srChoiceDescription=365834),AchievementID=ACHIEVEMENT_43_DLC7_BROKERDEFEAT,PowerImage="SB_Codex_Images.Stasis_512")
i.e. change AchievementID=56 to AchievementID=ACHIEVEMENT_43_DLC7_BROKERDEFEAT
The reason that the Bonus Talents are not available for new characters is because the BioGuiResources.ini file was removed from the Kasumi DLC (this enabled the Inferno Grenade and Flashbang Grenade Bonus Talents for New Characters, but not Stasis)
There is a bug-fix Mod on NexusMods that will make Stasis available from Advanced Training, and also make all 3 DLC Bonus Powers available for New Characters, if you have unlocked them.
