I don’t think comparisons with past performance are necessary the most relevant when considering the growth of religious groups. I find it more interesting to compare religious groups with each other at any given time because all religious groups are subject to the same society-wide forces of secularisation in the modern on age.
That being so, in western countries such as the UK, the US, Canada, Australia and New Zealand, the growth of Seventh-day Adventists could fairly be described as very good in recent decades; the growth of Jehovah’s Witnesses as good; the growth of Mormons as poor; and the growth (actually decline) of many other religious groups (ranging from Presbyterians to Unitarians to Anglicans) as very poor, or extremely poor.
The growth of Seventh-day Adventists and Jehovah's Witnesses may be down from the past, but both groups are doing very well in terms of growth compared with other groups. In a situation where many religious groups are shrinking by between 1 and 5% per year, should a 1 or 2% average annual growth really be viewed as a failure or any cause for alarm?