Using wrapper class to update multiple objects in dataTable

I'm fairly new to this, so I apologize if this is an obvious question, but I haven't been able to find answers after an extensive search. Thanks in advance for your help!

I have a dataTable that contains inputfields for multiple objects (all saved to a very basic wrapper class that I hopefully set up correctly) and some columns are only rendering if a specific value is selected in the selectList. My problem is that when I save the fields, everything is coming through as null even if a value is entered (I instantiated the fields in my wrapper class to test and the instantiated values replace null, so I'm wondering if I have something wrong with the order?).

Here are a couple brief snippets of what I believe is the applicable code.

Visualforce (not in it's entirety, let me know if I need to provide more):

<apex:form >
    <apex:actionRegion >
        <apex:pageblock id="pb">
            <apex:dataTable value="{!lstInner}" var="e" columns="9" id="taskTable" headerClass="sectionHeader" width="100%">
                <apex:column rendered="{!renderActivity}">
                    <apex:facet name="header">Subject</apex:facet>
                    <apex:inputfield value="{!e.myActivity.Subject}"/>
                </apex:column>
                <apex:column> <!--ALWAYS RENDERED AND USED FOR myActivity AND myOtherActvity IN CONTROLLER-->
                    <apex:facet name="header">Subject</apex:facet>
                    <apex:inputfield value="{!e.myActivity.Description}"/>
                </apex:column>
                <apex:column rendered="{!renderOther}">
                    <apex:facet name="header">Subject</apex:facet>
                    <apex:inputfield value="{!e.myOtherActivity.Subject}"/>
                </apex:column>
            </apex:dataTable>
        </apex:pageblock>
    </apex:actionRegion >
</apex:form >

Controller and wrapper (not in it's entirety, let me know if I need to provide more):

public with sharing class MyController{
    public MyController() {
    lstInner = new List<innerClass>();
    }

    public class innerClass {      
        public String recCount {get; set;}
        public Activity myActivity {get; set;}
        public OtherActivity myOtherActivity {get; set;}

        public innerClass(){
            myActivity = new Activity();
            myOtherActivity = new OtherActivity ();
        }

    public PageReference save() {
        if (lstInner.size() > 0){
            for (Integer a = 0; a < lstInner.size(); a++){
                if (lstInner[a].myActivityType == 'Other'){               
                    OtherActivity oa = new OtherActivity();
                    oa.Subject = lstInner[a].myOtherActivity.Subject;
                    oa.Description = lstInner[a].myActivity.Description;
                } else if (lstInner[a].myActivityType == 'Activity'){               
                    Activity a = new Activity();
                    a.Subject = lstInner[a].myActivity.Subject;
                    a.Description = lstInner[a].myActivity.Description;
                }
            }
        }
    }
}