I am having similar experience, particularly when it comes to uploading leads or using a single flow action for updating lead record details. I uploaded a list with one single lead record in it and it took just under 4 minutes to get the final confirmation box saying lead successfully uploaded. There is a support ticket raised for this and Jordan escalated it with his support team so hopefully they will fix this soon.
Clearly this is a huge issue for the community. Things like merging lead records also take 5-10 minutes most of the time. Most of our smart lists take 2-3 minutes to load and we have a tiny DB (< 100k). Lately even looking up a single record is taking 3-5 minutes, especially in the late afternoon Pacific time (when support is unavailable to witness it -- sigh). Orion is supposed to help:
Orion might be helping with things like trigger evaluation, but the general speed of Marketo as a user is always a bit painful - especially loading smart lists and reports. We haven't seen that improve.