Well, Meww made good points, but Dante isn't gonna read a brick wall like that. Here, I'll give my opinions.
For the people who play senju and may not know how it feels to fight one I'll walk you through it. Basically you hit them and you are autobinded, they imediately burial you binding you for about 3 seconds longer. The bind alone does about 500 damage, they then follow with wood drills which does another 500 damage. For my Clay, it's already in critical. (This was over a span of about 3 seconds, all of which I could not move, sounds fun right? Wait it gets better.) If by some miracle I'm not dead they use wood grave, now I'm trapped in a jutsu that would kill me if I walk around (Remember I'm in critical) So I can still not move. After this is over with I can finnally attack again if I'm alive.
Now I attack the senju again and right before I do they use Deep Forest Emergence, (Sure I can get out but it will still take some time especially in critical.) which traps me in this poison thing that does dot in its area, the damage isn't op but with my hp already in Critical I'm probably gonna die. If by some miracle again I don't die and finally hit them (Yes, after all of this I finally get a hit in.) they are gonna activate four pillar jutsu, this jutsu will basically stun me again, heal the senju, and allow them to do whatever they want to me. The jutsu alone has the ability to do from 200-1500 hp depending on if you are hit or not.
Now, what if the senju is a pro? He'll do just this and basically ohko anyone. Wait to get hit, then use 4 Pillars jutsu and use Deep Forest Emergence and Wood Grave while you are inside 4 pillars. While binded from the auto bind they will burial you and use wood drills. Now while they wait for all of their damage over time aoe jutsus to take affect they can either use their trees to heal, or use Sage Mode and punch the hell out of your binded ass. I mean they have 3 aoes that all can be used to bind the opponent in place and are basically unavoidable, Forest Emergence, Wood Grave, and 4 pillars. If used at the same time they put the opponent in a position where they cannot do anything at all. All while the Senju can basically dish out over 2000 damage if they use all of their other techniques. Most clans don't even get 2000 hp.
Let me explain why they are how they are.
Please Read
Think really hard here...
How many jutsus do senjus have that are aoe? 3
Do any of these jutsus have weak unqiue effects because of the fact that they're aoe? No
How many of their jutsus limit the opponent's movements in any way? 4
Do any of these jutsus do less damage as a result of limiting movement? No
How many of their movement limiting jutsus are unavoidable? 3
Are any of their jutsus at all hard to hit with? No
Is aiming involved with this clan? No (I mean most of the time you are just waiting for your opponent to hit you, right?)
Are there any useless jutsus with this clan? (Think about it, every clan has one.) No
Questions for you guys to answer for yourselves...
Why is it that this clan is the only clan in the game with 3 aoes?
Why can they "bind" you without doing anything productive to deserve the bind?
Why is their damage, despite all of those other perks, some of the highest in the game?
Despite all of this, why can they heal themselves on top of all that?