I'm answering from Germany. As a matter of fact the arrangers have become the most normal things for musicians performing in the field of entertainment/ dance music. Only the more "conceited" high-browed studio musicians don't want to admit that they also sometimes use arrangers. A friend of mine owns a studio and produces jingles for local adverisements. Whenever he is short of time or ideas he goes for the good old X1.
But coming back to the main point. I started playing dance music back in 1982. At first we were three in the band. Keyboard, guitar and drums. Me, on the keyboard, playing the bass lines with my left hand. Then since 1986 we started to perform as a duo, consisting of keyboard/ guitar. The first keyboard I used for this was a Yamaha PS 6000 with a Korg Poly 61, a Korg DW 8000 and a DX 21. Next was a Solton TS 4, a accompaniment-machine with only three octaves just for playing accompaniment patterns. I used this together with a DX7 and a Korg T3. When the sound of the arranger keyboards became much better I sold my sythies and went for two arrangers. Nowadays I am playing the Solton MS 100, predecessor of the X1 and the Roland G1000.
Definitely more than 90 percent of the musicians who play dance music at parties are nowadays using arrangers nowadays. We for example sometimes play gigs with four musicians without a drummer. We have keyboard, guitar, western-guitar/ trombone and trumpet/percussion in this case. It's sad but most of the hotels don't even have the space for a large band with a drumkit anymore.
Best wishes from Germany
Markus

PS.: I've heard rumours about a new keyboard from Solton which is to be presented at the Frankfurt Music Fair next year in March. As soon as I get to know more I'll post a note about it.