Yeah a lot of what he is saying is either wrong or supposition. He mentions power levels but clearly hasn't looked in depth into how they actually affect various abilities and ends up over valuing them. He also talks about the powerful high tier abilities despite the fact that in PoE these were often lacklustre and highly effective builds could easily be made that didn't use them.
Also: "it can make early parts of the game harder until you're all geared up" - I think, if anything, multiclass characters will have an easier time in the early game as many of the basic abilities of a class are very powerful. I'll take having both Sneak Attack and Soul Whip over access to power level 2 and 3 abilities earlier any day.
beta testers have difficulty recalling what deadfire were like the first time they loaded up the beta. am recalling voiced consternation from any number o' players. with a couple o' months and possible dozens o' hours playing, deadfire doesn't play for a seasoned beta tester and hardcore poe fan the way it is gonna play for most folks. the video appears to be a "most folks" intro.
am recalling boeroer describing early struggles with deadfire until he understood the penetration mechanic. game became easy for him once he saw the numerous penetration exploits available, but first play weren't matching expectations based 'pon reading descriptions and listening to developer feedback. boeroer, last november, would be starting deadfire considerable ahead on the learning curve than the ordinary new player o' poe, but even he were confused by changes... and multiclassing offers more pitfalls than does penetration. build a bad multiclass is easy and if you is new player making reasonable assumptions based on reading ability descriptions to guide your choices, you could end up suffering for it.
the video is from november 20 2017, near two months ago, and is likely a better representation o' what new players will face as 'posed to beta tester feedback being offered here and elsewhere. sure, beta folks know how powerful is a few mc combinations. beta folks know which class synergies is effective and potent. *chuckle* now go back a couple months and recall all the wailing and hand ringing from some 'cause a paladin couldn't get sword and shield style w/o taking fighter... as if a barbarian/paladin needs sword and shield to be powerful in defense.
am not agreeing with all in the linked video, but the fact the video is from earliest beta is noteworthy.
HA! Good Fun!