except nobody uses tactical marines if it can be avoided competitively because their so god awful, most marines take them strictly as a requirement for something else in their army such as the mandatory troops picks of the CAD, given the choice they would use other things like marine bikes, assault marines, or sternguard. a more likely scenario would be my veterans charging bikes or scouts and now even if i kill them (which again is no guarantee since in the current meta those veterans would be built for shooting not cc) their just going to go kersplat thats to a conveniently placed plasma cannon or another really ugly marine squishing death gun.
and additionally crisis suits have good initiative and its difficult to get them to fail an I test, i think ive almost never seen them fail exiting a combat.
your overwatch numbers also dont figure in say playing against dark angels who have bs2, or bs4 overwatch
and theres plenty of units out there that pump out a lot more damage then tactical marines in a single vooley of shooting like eldar jetbike teams or hormagaunt blobs or imperial guard conscripts
so no your right the crisis suits are the worst case scenario for me to probably be using but really it only takes hit n run out of the equation all the other flow chart situations still happen, you fail charge for some reason and then die, you charge in and then die to the overwatch for one reason or another, you charge in kill the unit and then die because you cant capitalize on any victories you have locking in cc
i chose the crisis suits not for the fact that their a worst case scenario but because they cover all the bases, i could have easily used dark angel black knights being charged by khorne zerkers and be in more or less the exact same spot. or i could in theory say any space marine unit in a wierd one off's example since the land raider fucking excelsior is a thing (i know i own one). i could have used all sorts of other examples, and just because marines might live through and overwatch doesn't mean other units will like orks or tyranid lesser biomorphs like rippers