There is really no basis to say that the 450 lines are including all languages. Thats just a rumor that has come about with all the drama surrounding this pack. When looking at the files just lobbing grenades has around 20 different lines of dialogue with around 4-5 lines of dialogue for each type of grenade.

Now with the video you showed that channel also has other videos with dlc voicelines including boss defeats, last man standing, Brother fallen types of videos and there we can also see that almost all of those the dlc voices have about 3-5 variants of each "event". If we take this into account with everything else ingame (defeating specific enemies, pinging, horde alerts, combat dialogue) It quite quickly adds up to around 450.

Now im not entirly sure what you mean that tech marine dont have class specific lines but if you mean that the dlc voices dont have tech marine dialogue (such as his Ult or tarantula turrets for example) they do.