ECG is absolutely used in the diagnosis of heart failure. Dialated cardiomyopathy can take the form of concentric where the cardiomyocytes significantly hypertrophy or eccentric hypertrophy where the stretch of the ventricle cant cope and significantly dilates (see Starlings laws). In both cases the ventricle appears large on xray however, more so in the latter case.
It is very important to know the stage of CHF. Ie: chronic (early or late stage) or following MI (chronic on acute). The ECG picture will vary accordingly but some things will stay with the patients ecg pattern indefinately.
The picture you give here is just one of many. For example in late stage heart failure, the heart decompensates due to a massive after load on the heart caused by sympathetic hyperactivity. In this case, you may well see a widened pathological qrs but you will certanly see a drop in the qrs height (relative to their prior ecg).
In the case of concentric hypertrophy of the ventricle the qrs wave will remain high but the ventricular ejection fraction will be low due to the cardiomyopathy effecting the end diastolic volume. So the clinical picture needs to accompany the ECG.
Hope this helps