Many years ago – SCOM was updated to have better granular control over Notification Subscriptions in the UI. We saw many improvements using controls based on group, class, specific rule or monitor, along with other criteria:
However – the Product Connector subscription wizard was never updated. 
This is unfortunate, because both product connectors and email notification subscriptions are actually identical behind the scenes. The UI is just a wrapper to create XML. The modules behind the scenes are the same: Microsoft.SystemCenter.SubscribedAlertProvider
You are not limited by the UI’s limitations, however. While more time consuming – you can use the same criteria and expressions in product connectors, as you would in an email notification. One of the simplest “tricks” to making this easy, is to create a disabled notification subscription that mirrors each product connector subscription you want – then export the Microsoft.SystemCenter.Notifications.Internal MP (Notifications Internal Library), and copy the expressions over to your product connector subscriptions. Then simply increment your notifications internal library MP version, and reimport. (Always save a backup first!)
Here are some common examples:
Class (raised by ANY instance of a given class):
<Types> <TypeId>7d5bddb4-c5c3-ee48-c42a-4c8d047825d0</TypeId> </Types>
Group (raised by any instance contained by the group):
<Groups> <GroupId>457c209e-d14b-0721-be20-c3bf55447dab</GroupId> </Groups>
Specific instance of a class (raised by a single specific instance of a specific class):
<Criteria> <Expression> <SimpleExpression xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <ValueExpression> <Property>BaseManagedEntityId</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>20a8fddb-88f6-1329-4771-0c4f73279542</Value> </ValueExpression> </SimpleExpression> </Expression> </Criteria>
Monitor and Rule (note the OR):
<Criteria> <Expression> <Or xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Expression> <SimpleExpression> <ValueExpression> <Property>ProblemId</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>b59f78ce-c42a-8995-f099-e705dbb34fd4</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>RuleId</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>8060f053-dc84-330d-c7d0-3c659f9b7ca7</Value> </ValueExpression> </SimpleExpression> </Expression> </Or> </Expression> </Criteria>
Specific rule, and only a specific instance of a class (note the AND)
<Criteria> <Expression> <And xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Expression> <SimpleExpression> <ValueExpression> <Property>RuleId</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>8060f053-dc84-330d-c7d0-3c659f9b7ca7</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>BaseManagedEntityId</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>20a8fddb-88f6-1329-4771-0c4f73279542</Value> </ValueExpression> </SimpleExpression> </Expression> </And> </Expression> </Criteria>
All the other typical criteria stuff:
<Criteria> <Expression> <And xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Expression> <SimpleExpression> <ValueExpression> <Property>Severity</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>2</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>Priority</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>2</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>ResolutionState</Property> </ValueExpression> <Operator>Equal</Operator> <ValueExpression> <Value>249</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>AlertName</Property> </ValueExpression> <Operator>Like</Operator> <ValueExpression> <Value>%foo%alertname%</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>AlertDescription</Property> </ValueExpression> <Operator>Like</Operator> <ValueExpression> <Value>%foo%description%</Value> </ValueExpression> </SimpleExpression> </Expression> <Expression> <SimpleExpression> <ValueExpression> <Property>CustomField1</Property> </ValueExpression> <Operator>Like</Operator> <ValueExpression> <Value>%footextincustomfield%</Value> </ValueExpression> </SimpleExpression> </Expression> </And> </Expression> </Criteria>