In all the cases of Kamui snipe warping "instantly", they were all very close to Kakashi. Note: I will use even unskilled Kamui Kakashi to prove my point too.
Lets look at all the long range use scenario.[
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].<--2 more pages, you get the point. Now lets look at the close range in the same arc[
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. Techically 2 pages compare to long range 5 pages. Lets look at more experience Kakashi via Pain arc. [
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]. Thats it 1 page for close range. Now lets look at long range[
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]<== Page 1 give it alot more panel time. Lets look at War arc: Long range [
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[/URL]>
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]. Obito had enough time to cancel it. In fact the whole fight Kakashi shown he had to move closer to warp things faster, shown through out the whole fight. Juubi arc Kakashi's comment[
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]. Close range Juubi arc[
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. All of these evidence shows that close range shot of Kamui's line of sight is slower then long range shots, therefore it isn't instant in ever range. Even if Kakashi were to make a larger warp range, that would mean it will take longer to consume the opponent, shown against Deidara. [
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].
In the end these one shot "instant" jutsu have its cons
