According to you, the anime shouldn't be used at all. The manga shows him using but one hand seal.Water Wall is only 5 hand seals.
But yea I stand corrected, the anime had him using 3 hand seals, you're right.
Furthermore, even his Water Dragon takes a lesser amount of hand seals than Zabuza's, and just from displaying these two jutsu (the only two Tobirama has ever displayed in the manga), ANBU already considered his ninjutsu Kage-level, and after displaying one jutsu, it already qualified as Kage-level in Orochimaru's books:
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"During this technique's first appearance, forty-four hand seals were used to perform it; the highest amount of hand seals necessary to use a technique shown in the series so far. However, later appearances of the technique have implied that the exact number of seals required isn't fixed."
"The ideal place to use it is near a body of water, but if the user's skill allows it, it is possible to use it even in a place where there is none."