Measurement of the X-ray spectra of the He-like Ni ions (Ni26+) and their dielectronic satellites (Ni25+, Ni24+, and Ni23+) plays a crucial role in determination of electronic and ion temperature of plasma in the JET device. Because n >= 3 satellites of Ni25+ overlap with resonance line of Ni26+, it is important to reconstruct the structure of these satellites reliably. It is especially important in the cases when plasma rotation is high whichmay result in an additional broadening of the resonance line. This work is an attempt to identify possible causes of the additional broadening of the resonance line due to the effect of overlapping the dielectronic satellites with the resonance line of Ni26+ and the effect of toroidal plasma rotation shear.