This Unit is very powerful in Dark Irregulars decks. If you call one before, or directly after riding Decadent Succubus, and then call a number of other Dark Irregulars, you can give her a massive one-turn power boost.
This Unit is ideal behind a Vanguard Demon Eater and Stil Vampir. Their skills will cause her to gain a steady 3000 Power each turn, allowing them to hit for at least 21000.
Alluring Succubus can be used at later turns to bring Doreen's power up, if you do not have a more suitable method or need to cross a higher threshold.
If you plan on using the effect of Demon World Marquis, Amon, having a Doreen on the field can be extremely beneficial, as she will gain power for every Unit you move to the Soul.
Even if Doreen requires a Dark Irregulars Vanguard, she does not need the Units moved to the Soul to belong to that clan, making her viable in mixed decks, more specifically some Kagero builds utilizing Amon.