Question

Are DEPT techniques important for structural elucidation?

Answer 1

Yes Absolutely

Explanation:

The technique DEPT gives similar information to an 'Off-resonance decoupled spectra' (one bond `C-H` couplings are retained so the single for a particular `C` is given by the number of `H` bonded, `n+1` rule, eg. for a `-CH2-` we would see a triplet).
Without going to deep into the physics DEPT is performed by a sequence of pulses with different delay times to create a DEPT spectra. This would result in identification of `-CH_3` and `CH`, these would appear as a normal peak pointing upwards. And the `-CH_2-` group would appear as an inverted peak.
This would make it possible to figure out how many H there are bonded to C.
So DEPT would often be performed together with an 'Off-resonance decoupled spectra', making it easy to detect the different `C-H` groups.