To me it is clear, Azure App Services is an application platform providing the tools and runtime services to quickly build modern, distributed solutions. Modern, because it uses APIs. APIs should be used, because Data Services, 3rd party APIs and SaaS Applications are built on that paradigm. And that paradigm facilitates agile solution development and quick time to market. Creating a modern, distributed, composite solution is using all the different building blocks provided by the iPaaS platform and the SaaS applications, Data Services and 3rd party APIs (for example the ones listed in programmableweb.com or the Azure Marketplace).
In my opinion, we should only use public cloud based legacy integration paradigms for hybrid purposes. That is, bridging on-prem soap services to cloud based API integration layers. We should not bother about providing traditional EAI and B2B like integration paradigms. Forget about Batching EDI messages, transaction scopes and stuff like that. I’d say, just boycot that in the public cloud. Just rely on idempotency of the independently deployed APIs. And provide an on-premises server solution for the legacy integration stuff. We shouldn’t be building ESBs in aPaaS. We should be building distributed solutions based on modern paradigms.