Use of evidence-based treatment and its limitations
One of the current challenges faced by many survivors of complex trauma (or developmental trauma disorder) is support for treatment since many of the current therapies are relatively expensive and not all forms of therapy or intervention are reimbursed by insurance companies who use evidence-based practice as a criteria for reimbursement. Cognitive behavioral therapy, prolonged exposure therapy and dialectical behavioral therapy are well established forms of evidence-based intervention. These treatments are approved and endorsed by the American Psychiatric Association, the American Psychological Association and the Veterans Administration. While standard evidence-based treatments may be effective for treating standard post-traumatic stress disorder, treating complex PTSD often involves addressing interpersonal relational difficulties and a different set of symptoms which make it more challenging to treat. The United States Department of Veterans Affairs acknowledges,

the current PTSD diagnosis often does not fully capture the severe psychological harm that occurs with prolonged, repeated trauma. People who experience chronic trauma often report additional symptoms alongside formal PTSD symptoms, such as changes in their self-concept and the way they adapt to stressful events. For example, "Limited evidence suggests that predominantly [Cognitive behavioral therapy] CBT [evidence-based] treatments are effective, but do not suffice to achieve satisfactory end states, especially in Complex PTSD populations." Treatment challenges
It is widely acknowledged by those who work in the trauma field that there is no one single, standard, one size fits all treatment for complex PTSD.
There is also no clear consensus regarding the best treatment among the greater mental health professional community which included clinical psychologists, social workers, licensed therapists MFTs) and psychiatrists. Although most trauma neuroscientifically informed practitioners understand the importance of utilizing a combination of both top down and bottom up interventions as well as including somatic interventions (sensorimotor psychotherapy or somatic experiencing or yoga) for the purposes of processing and integrating trauma memories. Survivors with complex trauma often struggle to find a mental health professional who is properly trained in trauma informed practices. They can also be challenging to receive adequate treatment and services to treat a mental health condition which is not universally recognized or well understood by general practitioners. Allistair and Hull echo the sentiment of many other trauma neuroscience researchers (including Bessel van der Kolk and Bruce D. Perry) who argue: 

Complex presentations are often excluded from studies because they do not fit neatly into the simple nosological categorisations required for research power. This means that the most severe disorders are not studied adequately and patients most affected by early trauma are often not recognised by services. Both historically and currently, at the individual as well as the societal level, "dissociation from the acknowledgement of the severe impact of childhood abuse on the developing brain leads to inadequate provision of services. Assimilation into treatment models of the emerging affective neuroscience of adverse experience could help to redress the balance by shifting the focus from top-down regulation to bottom-up, body-based processing."