Marketing Channel is a dimension... it's basically an eVar with a 30 Day expiry... it's just being set via Rules instead of in your Launch.
You cannot change the attribution on those metrics, but I don't think you have to in this case... let's look at an example:
Visit 1:
- Page 1 (Campaign cid=google_paid)
- Marketing Channel = "Paid Search"
- Marketing Channel Detail = "google"
- Marketing Channel Instance triggered
- Page 2
- Marketing Channel retains value "Paid Search"
- Marketing Channel Detail retains value "google"
- Marketing Channel Instance not triggered
- Purchase Made
- Page 3 (Campaign cid="social_yyy_paid")
- Marketing Channel = "Paid Social"
- Marketing Channel Detail = "yyy"
- Marketing Channel Instance triggered
- Page 4 (Campaign cid="newsletter_xxx")
- Marketing Channel = "Newsletter"
- Marketing Channel Detail = "xxx"
- Marketing Channel Instance triggered
Visit 2:
- Page 5
- Marketing Channel retains value "Newsletter"
- Marketing Channel Detail retains value "xxx"
- Marketing Channel Instance not triggered
- Purchase Made
| |
Page Views |
Visits |
Unique Visitors |
Marketing Channel Instance |
Orders |
Orders (Participation) |
| |
5 |
2 |
1 |
2 |
2 |
2 |
| Paid Search |
2 |
1 |
1 |
1 |
1 |
1 |
| Newsletter |
2 |
2 |
1 |
1 |
1 |
1 |
| Paid Social |
1 |
1 |
1 |
1 |
0 |
1 |
The Marketing Channel will apply to each page view it touches... "last touch" doesn't mean that the history of the hits will be re-written... the last value that was set (and maintained) when that page view occurred will be used (i.e. Page 2 and Page 5).
Same with Visit and Unique Visitor... all the values that were set within a Visit, or touched by a Visitor will be associated to those metrics... there is no need to use custom attribution.
If you need to see only the hits where the "Marketing Channel" was set, you can use "Marketing Channel Instance".
Orders, however, if you want to see all the channels that lead up to an order, you need the custom attribution so that you aren't just looking at the "last" value, you are seeing all. Note, since I really only deal with subscription models... so I don't have multiple orders within an applicable window, I might be undercounting the participation... it might also include the channels before the first purchase since they are within 30 days... but the point I am really making here is that because "Orders" (like PVs) is a set point in time, it needs custom attribution to get all the touchpoints... PVs don't, as every PV will already have a channel associated to it...