We see this problem all too often.
Electric heating is all very well until there's a power cut.
I have difficulty in analyzing what "all" modifies in both sentences 1 and 2, and in understanding what "all" means in other words when used in 1 and 2.
To me, "all" is used to put an emphasis on "too" and "very", so "all" seems to modify "too" and "very".
And "all" doesn't seem to modify the entire "too often" and "very well", since "all often" and "all well" don't make full sense.
fire1 We see this problem all too often. The phrases: all too soon all too often and all very well are idioms. com/dictionary/all%20very%20well
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fire1We see this problem all too often.
The phrases:
all too soon
all too often
and
all very well
are idioms.
https://www.merriam-webster.com/dictionary/all%20too%20often